Sauté shrimp and scallops with olive oil, garlic, salt, pepper, and chili flakes for 1 minute, then turn, add mussels and whole clams, and sauté for another minute or so until clams start to open.
Deglaze with wine and add chopped clams with their liquid. Cover skillet and steam until mussels are opened (discard any unopened ones) and the liquid has reduced by half. Add butter and parsley and simmer until incorporated.
Serve in a hot skillet or toss with cooked pasta and garnish with more parsley.