Melt the butter in a large deep skillet over medium high heat. Pat the shrimp dry with paper towels. When the butter is melted and the pan is very hot, add the shrimp, in one layer without crowding, and cook about 1 minute per side until shrimp is pink and slightly curled. You do not want to overcook shrimp as they will finish cooking in the sauce. Remove and set aside.
Reduce the heat to medium and add the leeks and garlic to pan drippings. Cook until fragrant. Add the mushrooms and continue cooking until the mushrooms are soft and begin to lightly brown, about 3-4 minutes. Add the white wine and lemon juice and continue cooking until about half of the liquid has evaporated, about 3-4 more minutes.
Add both cans of shrimp paté, heavy cream, salt and pepper to the pan. Bring to a boil and continue to cook stirring until the paté has ‘melted’ into the sauce the consistency is smooth and velvety, about 5 minutes. Add the shrimp (with any juices that have developed), peas, and parsley to the sauce. Fold in the linguini and toss to coat.
Serve hot in bowls garnished with more parsley and a sprinkle of grated Parmesan cheese.