The Best Chocolate Lava Cakes

INGREDIENTS 4 ounces semisweet baking chocolate, chopped 2 tablespoons unsalted butter, at room temperature, plus more for greasing custard cups 2 tablespoons sugar, plus more for the custard cups 2 large eggs 2 tablespoons all-purpose flour 1/8 teaspoon kosher salt PREPARATION  Preheat oven to 425°F, and grease two 6 to 8-ounce custard cups or ramekins…