Melt butter in a large skillet over medium-high heat. When butter foams, add shrimp, shallot and garlic. Season with salt and pepper and sauté until shrimp are just opaque and cooked through, 2 to 3 minutes. Immediately transfer to a plate to cool.
When shrimp are cool, transfer to a food processor. Pulse with lemon zest and scallions until chopped but still chunky.
In a large bowl, combine mayonnaise and sour cream. Add lemon juice, hot sauce and parsley. Stir in shrimp mixture and season with additional salt and pepper. Cover and chill for at least 1 hour. Taste and adjust seasoning. Serve with crudités, pita chips or crackers, if desired.