1. Let some air out of the potato chip bag and then crush the bag with a rolling pin or wine bottle to make fine crumbs. Transfer the chip crumbs to a large bowl and add the salmon, ricotta and Old Bay Seasoning. Finely grate the zest from the lemon and add it to the bowl (reserve the zested lemon). Stir the mixture well to combine, really breaking up the salmon as you mix.
2. Divide the mixture into 8 equal portions and use your hands to form each into a patty. It’s helpful to divide the mixture in half and then in half again, and so on, to make sure the patties are the same size.
3. In a large nonstick skillet over medium-high heat, melt the butter. (If you think you may need to work in two batches so the fish cakes all fit and can be easily flipped, melt half the butter the first time and remaining butter, the next.) Once the butter begins to bubble, place the fish cakes in the skillet and cook without moving them until their bottoms are nicely browned, 2 to 3 minutes. Using a spatula, carefully flip each cake over and cook until nicely browned on the other side, another 2 to 3 minutes. Transfer the fish cakes to a plate and cover with foil to keep warm.
4. Increase the heat to high under the skillet and add the peas, half-and-half and salt. Cook, stirring, just until the peas are bright green and tender and the half-and-half has reduced slightly, about 4 minutes. Transfer the saucy peas to a serving platter and place the fish cakes on top. Cut the zested lemon into wedges and serve the wedges with the fish cakes for squeezing over.

NOTE: To make your own Old Bay substitute, in a small bowl, stir together 1 teaspoon of each kosher salt, sweet paprika and garlic powder.

MAKE AHEAD: The fish cakes can be assembled up to 3 days in advance and refrigerated until ready to cook.

STORAGE NOTES: Leftover fish cakes can be refrigerated for up to 3 days. Reheat in a 300-degree oven for about 10 minutes or until warmed through.