Heat oven to 425°F. Tear 4 large sheets of parchment paper.
On one sheet of parchment, place 1/4 of the asparagus parallel to the long ends, leaving at least 2 inches at the top and bottom of the asparagus. Season asparagus with salt and pepper. Place 2 lemon slices on top of asparagus, and top with a fish filet. Squeeze lemon over fish and with salt and pepper. Place a small pat of butter on top of fish.
Fold the parchment into a packet by folding the two long sides to meet together above the center of the fish. Fold and crease parchment three times to seal. Then fold each short end up and crease 2-3 times to seal. Repeat with remaining parchment, asparagus and fish to make 4 packets.
Place packets on a baking sheet and bake 12-15 minutes, or until fish is cooked through.
While fish is baking, make the herb sauce. Finely chop parsley, chives, dill, and garlic. Add to a bowl. Add lemon zest, lemon juice, vinegar, olive oil, salt and pepper. Stir to combine.
Once fish is done, carefully open packets and discard lemon slices. Spoon sauce over fish and serve.
You can swap any of the fresh herbs out for whatever herbs you have on hand.