For the Crab Mix
2 tablespoons unsalted butter
2 pounds yellow onions, finely diced
1/4 cup finely diced celery
1/4 cup finely diced green bell pepper
1 bay leaf
1 cup heavy cream
1 pound boiled or steamed crabmeat
1/2 cup peeled boiled shrimp
2 tablespoons finely chopped green onion
2 tablespoons finely chopped fresh flat-leaf parsley
1 teaspoon kosher salt, plus more as needed
3/4 teaspoon cracked black pepper, plus more as needed
1/4 teaspoon cayenne pepper, plus more as needed
2 tablespoons hot sauce, preferably Original Louisiana Hot Sauce, plus more as needed
1/2 lemon, plus lemon wedges for serving
For Dredging and Panfrying
2 cups fine cornmeal, preferably freshly milled
1 tablespoon kosher salt
1/2 teaspoon cayenne pepper
Clarified butter (see Note) or canola oil
Warm a heavy-bottomed Dutch oven or a cast-iron skillet over medium heat for 2 minutes, then add the butter. When it has melted, add the onions and cook, stirring occasionally, until soft and translucent, about 20 minutes.
Add the celery, bell pepper, and bay leaf and cook, stirring occasionally, until the vegetables are very soft with no bite remaining, about 20 minutes. Taste a piece of bell pepper—if the vegetables are ready, there should be no more crunch to it.
Add 1/2 cup (120 ml) of the cream, stir, and reduce the heat to low. Cook until most of the cream has reduced, about 8 minutes, then add the remaining1/2 cup (120 ml) cream and simmer until the liquid has completely reduced and thickened to the consistency of a paste, 20 to 30 minutes. (It’s important to reduce the liquid as much as possible, or the mix will be watery.) Turn off the heat, transfer the mixture to a large bowl, and let cool.
While the mixture is cooling, put your crabmeat in a large bowl and use your fingers to carefully pick through it and remove any crab shells: Take a little crab at a time and lightly rub it between your fingers—you should be able to feel bits of shell. Go through the meat before using.
Pulse the shrimp in a food processor until finely ground. Add the ground shrimp to the cooled onion mixture and stir well. Add the crabmeat, green onion, and parsley. Season with the salt, black pepper, cayenne, and hot sauce and a squeeze of lemon juice and stir to combine. Taste the crab mix and adjust the seasoning to your liking.
Dredge and fry the crab cakes: Put the cornmeal in a shallow bowl and season with the salt and cayenne. Dip a 1/2-cup dry measuring cup into the cornmeal to lightly dust the cup. Fill the cup with the crab mix and tap the portion out into your hand. Coat the disk of crab mix liberally with the cornmeal on both sides and use your fingers to press and turn the disk in your hand, forming it into a hockey puck that is a little wider than the measuring cup and about half as thick as its depth. Be sure to flatten both the top and bottom for even cooking. Be liberal with the cornmeal so the crab mix doesn’t stick to your hands as you form the cakes. With practice, you’ll be able to form them with a few quick turns of your hands and fingers. Set the crab cake aside on an oven tray or a large plate and repeat with the rest of the crab mix. Each crab cake should weigh a tad under 4 ounces (115 g).
Warm a large heavy-bottomed nonstick sauté pan or a well-seasoned cast-iron skillet over medium-high heat for about 2 minutes, then fill the pan with clarified butter to a depth of 1/4 inch (6 mm)—it should come one-quarter of the way up the crab cakes when you add them to the pan. When the butter is shimmering, carefully place a few crab cakes in the pan in a single layer; don’t crowd the pan. The crab cakes should sizzle when they hit the butter. (Be careful not to burn yourself, as the butter will be hot.) Sear the crab cakes for 2 to 3 minutes on each side, until they’re crispy on the edges and golden on the top and bottom, with a slight crust forming around the whole thing. Use a fish spatula to remove the crab cakes from the pan and place on a paper towel–lined pan or plate to blot any excess oil. Serve immediately with a lemon wedge.