Step 1

Lay out catfish fillets in a single layer on a work surface and sprinkle with all-purpose seasoning on both sides; press seasoning into fish.

Step 2

Heavily coat the top side of the fish with blackening seasoning. Allow seasoning to sit until it begins to soak into the fish, about 10 minutes. Flip the fish over and repeat.

Step 3

Heat a large cast-iron or heavy-bottomed skillet over medium-high heat until you see a little smoke coming from it, 1-2 minutes. Add 2 tablespoons grapeseed oil and heat until shimmering but not smoking, about 1 minute; then add 2 tablespoons butter. Be sure the exhaust fan is turned on.

Step 4

Once butter is melted and bubbling, slowly lay in half the catfish fillets, angling them away from you to prevent spattering and being sure not to overcrowd the pan. Give the fish a little press with a metal spatula to be sure pieces are flat and in full contact with the pan. Cook fillets until browned and well crusted on underside and they release easily from pan (slide the spatula under them to check), 4-5 minutes. Then flip to cook second side to cook, an additional 4-5 minutes.

Step 5

Transfer fillets to a sheet pan lined with paper towels. Scrape out any burned-on spices from pan. Repeat to cook remaining fish, adding more oil and butter as needed.

Step 6

Serve hot with parsley scattered on top. Squeeze lemon wedges over fish if you like.