Pat the fillets dry and sprinkle lightly with salt and black pepper (not too much salt, because the prosciutto will be salty). Wrap two slices of prosciutto around each fillet, winding it around from top to bottom. Don’t worry if it doesn’t stick very well; it’ll contract and cling to the fish as it cooks. Set the wrapped fish aside.
Heat a 12-inch skillet with a lid over medium-high heat and add the olive oil. When the oil shimmers, add the salmon to the pan and cook until browned on the first side, about 2 minutes. Flip the fish over with a thin-edged spatula and cook the other side until browned, another minute or so. Transfer the fish to a plate. (It will not be fully cooked at this point.).
Add the onion and poblano to the hot pan and sauté until the vegetables begin to soften, about 2 minutes.
Add the corn, lima beans, cayenne and 1/4 teaspoon salt. Season with black pepper and sauté until the corn is almost tender, about 1 minute. Quickly pour in the cream and stir in the 1 tablespoon basil.
Top the vegetables with the fish, cover and reduce the heat to low. Cook until the fish is cooked through and flakes easily with a fork when pierced, about 3 minutes. Some of the salt from the prosciutto probably crept into the corn, so taste and season with more salt, pepper or cayenne if it needs it.
Mound the vegetables onto two warmed plates and top with the fish and a few basil leaves sprinkled over the top. Serve hot.