Cooking fish en papillote, or in a packet, is one of the best ways to cook it without odor. It’s incredibly fast and easy, and works with most fish fillets. It’s also a great... way to make a meal for one. The vegetables need to be cut very thin and small to cook quickly, julienning is the best way. It is traditional and healthiest to use parchment paper to make the packets, but foil can be used as well, and it is easier to handle, especially if having neuropathy in the hands. If the foil bothers you, try lining the foil packets with parchment paper. Making the packets may seem tricky, but it’s easy, so try again, if it didn’t work. Do not make the packets too small or tight; the fish and veggies will make steam as they cook, and need room to expand.
Diagonally slash the skin of each fish fillet three times. Set aside.
Tear off two squares of parchment paper or aluminum foil large enough to comfortably hold one fish fillet each. If lining the foil with parchment paper, make it the same size as the foil and lay it on the dull side of the foil.
Smear the center of the left side of each foil/parchment square with 1 teaspoon of oil. Divide the leeks, carrots, and garlic into two equal amounts and lay on top of the oil on each square. Lay the fish fillet, skin side up, on top of the vegetables. Top with some slices of tomato and sprinkle equally with the lemon zest, the fennel seeds and some salt.
Fold the foil in half over the fish and tightly roll the sides of the packet together to seal, starting from the fold, leaving a small gap open at the far side. The packet should have the look of a giant empanada. Pour the lemon juice mixture through the gap into each packet and then seal it completely. Lay the packets on a cookie sheet and bake in the oven for 10-15 minutes, depending on the thickness of the fish. Let them sit for a moment before opening.
Carefully open the packets -- there will be steam! You can plate the fish and vegetables or serve them in the half-open packets. Sprinkle with chives.
If on a bland diet, omit or deseed the tomato slices. And either pass on the garlic or simply discard it before eating since it does give the fish and veggies great flavor