Tilapia in Parchment with Mushrooms and Thyme
Browned mushrooms and shallot sealed into parchment packets under tilapia fillets, so the fish steams in mushroom juices and each packet opens onto its own small pool of sauce.
Why You'll Love This Recipe
Parchment packets have a reputation for being restaurant food, and they are actually the least demanding way I know to cook fish on a weeknight. There is one skillet for the mushrooms and then no pan at all, because the paper takes over. Each person gets a sealed packet that comes to the table puffed and browned at the edges, and cutting it open sends up a cloud of thyme and mushroom steam that does more for a Tuesday than it has any right to. I do this most often in fall, when the mushrooms at the store are cheap and everything else in the kitchen is a root vegetable.
The one step that cannot be skipped is browning the mushrooms first. Raw sliced mushrooms are mostly water, and if they go into the paper straight from the cutting board they release all of it and the packet turns into a puddle with a poached fish in it. Eight minutes in a hot skillet drives that water off and concentrates what is left into something deeply savory, and then the small amount of liquid they give up in the oven becomes a sauce rather than a flood. Fold the seams tightly, roll them over twice, and let the packets go a full twelve minutes without being opened to check.
Tilapia is mild and takes on whatever it is cooked with, which is precisely why it belongs here rather than a fish with opinions of its own. It comes out of the packet soft and white and tasting of mushroom, garlic, and thyme. The chives and lemon zest go on after the paper is open, so they land raw and sharp on top of something warm and earthy. If you are cooking for people who say they do not care for fish, this is the one I would put in front of them, because there is nothing about it that tastes of the sea.
Ingredients
- 4 tilapia fillets (about 6 oz each, 1 1/2 lb total)
- 1 lb cremini mushrooms, sliced 1/4 inch thick
- 2 large shallots, thinly sliced
- 4 cloves garlic, thinly sliced
- 3 tbsp olive oil, divided
- 1 tbsp fresh thyme leaves
- 1/4 cup low-sodium chicken broth
- 2 tbsp fresh lemon juice, plus the zest of 1 lemon
- 3 tbsp chopped fresh chives
- 1 tsp fine sea salt, divided
Instructions
- Heat the oven and cut the paper: Heat the oven to 400°F (200°C) with a rack in the middle. Cut four pieces of parchment about 15 by 12 inches and fold each one in half like a book, then open it flat again. The crease down the middle is what you will build against.
- Brown the mushrooms: Heat 2 tablespoons of the olive oil in a large skillet over medium-high. Add the mushrooms and 1/4 teaspoon of the salt and cook for 8 minutes, stirring only every couple of minutes, until the water they release has cooked away and the edges are browned. Crowding them means they steam, so use your widest pan.
- Add the shallot, garlic, and thyme: Lower the heat to medium, add the shallots, garlic, thyme, and another 1/4 teaspoon of salt, and cook for 3 minutes until the shallots soften and the garlic smells sweet. Pour in the broth, scrape the bottom of the pan clean, since everything stuck down there is the flavor the packets will steam in, and take it off the heat.
- Build the packets: Divide the mushroom mixture into four low piles, each on one half of a parchment sheet near the crease, so that the fish sits on a bed rather than against the paper and the packet has room to puff. Pat the tilapia dry, season with the remaining 1/2 teaspoon of salt, and lay a fillet over each pile. Spoon any juices from the skillet over the fish and drizzle with the last tablespoon of oil.
- Seal and bake: Fold the empty half of the paper over the fish and work around the open edge in small overlapping folds, pressing each crease flat, then twist or tuck the last corner underneath. Set the packets on a sheet pan and bake for 12 to 14 minutes, until they puff and the paper browns at the edges, since the puffing is the steam building inside and it is the clearest sign the seal is holding.
- Open and finish: Move each packet to a plate and cut it open across the top, keeping your face back from the first rush of steam. Scatter the lemon zest, lemon juice, and chives over the fish now rather than before it went in, because all three go dull in a hot oven and they are what make the plate taste fresh. It is done when the fillet is opaque all the way through and flakes at the press of a fork.
Variations
- Zucchini ribbons: Lay a few wide ribbons of zucchini over the mushrooms so they steam under the fish and add a soft green layer.
- Spinach underneath: Put a handful of raw spinach on the paper first, which wilts into the mushroom juices and makes the packet feel like a whole plate.
- Dill and orange: Swap the thyme for dill and the lemon for orange zest to push the packet sweeter and cooler.
- Mixed mushrooms: Use half cremini and half shiitake or oyster mushrooms for more texture and a deeper, woodsier smell when the packet opens.
- On the grill: Cook sealed packets on a covered grill over medium heat for about 14 minutes for a smoky edge to the paper and the mushrooms.
Storage & Leftovers
Leftovers keep in the refrigerator for up to 3 days. Lift the fish and mushrooms out of the paper and store them together with all the juices, since that liquid is what keeps a thin fillet from drying out between now and tomorrow.
Reheat covered in a low oven at 300°F (150°C) for about 8 minutes, or in a covered skillet over low heat with a spoonful of water. Tilapia is thin enough that a microwave will overshoot in seconds and leave the fish rubbery, so slow and covered is worth the extra time.
The packets can be built up to 8 hours ahead and refrigerated flat on the sheet pan, which is the whole reason I make this for company. Bake them straight from the refrigerator, adding 2 minutes to the time. Cooked packets do not freeze well, since the fish goes watery on thawing.
Notes & Tips
- Dry mushrooms brown better: Wipe them rather than rinsing them under the tap. Wet mushrooms sit and steam in the skillet and never take on the color that makes the sauce taste like anything.
- Use your widest skillet: A pound of sliced mushrooms needs room. Piled two deep they release water faster than it can evaporate and stay pale and squeaky.
- Fold the seams twice: One fold opens in the oven and lets the steam out. Small overlapping folds pressed flat, gone over a second time, keep the packet sealed and puffed.
- Pat the fish dry: Surface water on the fillets dilutes the sauce inside the packet. A quick wipe with a paper towel is all it takes.
- Sacrifice one packet: If you are unsure about timing, open one at 12 minutes and check it. The other three stay sealed and hot while you look.
- Open away from your face: The steam that comes out of a sealed packet is hotter than it looks. Cut a slit in the top first and let it vent before you open the whole thing.
Nutrition & Mindful Eating
- The fish, the mushrooms, and the shallot work as one thing inside the paper. The tilapia brings the protein, the mushrooms bring the savory depth and the liquid that becomes the sauce, and the shallot and garlic soften into both so the packet tastes seasoned all the way through.
- Tilapia is mild and fine-textured and cooks quickly, which makes it an easy fish to put in front of people who are unsure about seafood. It is dense with protein for how light it eats, and it carries selenium along with vitamin B12.
- Mushrooms browned hard in a skillet turn deeply savory, and that flavor comes from glutamates they produce naturally. They also carry B vitamins and, when they have been exposed to light, some vitamin D, which few other vegetables offer at all.
- Steaming in a sealed packet keeps every juice the fish and mushrooms release right there on the plate, along with the water-soluble vitamins that would otherwise pour down the sink with the cooking water.
- Chives and lemon zest scattered over the open packet stay raw and sharp, and that hit of fresh allium and citrus oil against the earthy mushrooms is what makes the dish taste finished with only a teaspoon of salt in the whole recipe.
- As you eat, take in the smell that comes up when the packet is first cut open, and let the softness of the fish against the meaty mushrooms be a reason to put the fork down between bites.
Frequently Asked Questions
Can I use foil rather than parchment?
Yes, and it seals more easily, though you lose the puffed paper at the table. Fold foil packets loosely so there is room for steam, and check the fish a minute early, since foil conducts heat faster than paper does.
Which other fish work in the packets?
Cod, halibut, trout, and sole all work. Anything thicker than about an inch needs 3 to 4 extra minutes, and sole or another thin flatfish needs about 3 fewer. Keep the mushroom layer underneath the same regardless of what is on top of it.
Do I really have to cook the mushrooms first?
Yes, if you want sauce rather than soup. Sliced mushrooms are mostly water and release all of it in a sealed packet. Eight minutes in a hot skillet takes that water out ahead of time and leaves you with concentrated flavor and a small pool of juices.
Does this fit an AIP elimination phase?
It does. Nothing here comes from grains, dairy, eggs, nuts, seeds, or nightshades, and the seasoning is shallot, garlic, thyme, lemon, and chives. Use plain parchment rather than a coated paper, and check the broth carton for pepper or added spice blends.