Three Onion Dip

Name: Three Onion Dip
Ingredients: 2 tablespoons plus 1 tsp. vegetable oil; 2 medium onions, thinly sliced; 2 anchovy fillets packed in oil, drained; 1 teaspoon mushroom powder (optional); 4 garlic cloves, finely chopped, divided; 4 scallions, green and white parts separated; Kosher salt and freshly ground black pepper; ⅓ cup mayonnaise; ⅓ cup plain whole-milk Greek yogurt; ⅓ cup sour cream; 1 tablespoon chopped fresh chives; 1 teaspoon Worcestershire sauce; Potato chips (for serving)