Sea Bass En Papillote

Preheat oven to 450 degrees F.

Cut parchment and fold each in half like a book. Trace a large heart half starting from the folded edge, then cut out and unfold. Repeat with remaining sheets of parchment.

Brush parchment with butter. Place 1/2 cup leeks on the right side of a parchment heart then top with a sprig of thyme. Season fish with salt. Top with a seasoned fish fillet.

Blend the mustard, wine, and pepper. Brush mixture on fillets. Top each fillet with 2 Tbsp shallots, 1/4 cup tomatoes, and 3 mushroom caps, then finish with a slice of lemon.

Fold the left side of the heart over the fish. Match the edges and begin folding at the top of the heart. Fold over 1/2" of edges, pleating at about every inch, making sure all edges match and folds are tight.

Once you've completed the folding once, make a double fold by folding and pleating again. Crease edges with your fingernail.

Place packets on two large baking sheets. Bake about 10 minutes (10 minutes per inch of fish). The packets will puff up; serve immediately or they'll deflate. Let each person tear open their packet.