When it comes to savory toasts, April Bloomfield has a firm set of beliefs: She likes her bread sliced thick and her toppings rich. At each of her three restaurants, bruschettas—as the Italians call them—are staples. At the Spotted Pig, warm chopped liver toast is a favorite; at the John Dory, it's anchovy and parsley; and at the Breslin, a seasonal combo of slow-cooked squash with burrata was a recent highlight.

For her final Slow Food Fast contribution, Ms. Bloomfield shares a recipe for crème-fraîche-coated mushrooms on...