LINE a loaf pan with aluminum foil. Make sure the tin foil goes up the sides of the pan, so the set fudge is easy to remove from the pan.

HEAT the chocolate chips, sweetened condensed milk, and butter in a medium-sized microwave-safe bowl on high for 1 minute.

REMOVE the bowl from the microwave. Stir the chocolate mixture with a silicone spatula until the chocolate is smooth. The residual heat should eventually melt all the chocolate chips. If necessary, microwave again in 10-second intervals. But take care not to burn the chocolate. Stir in the vanilla extract and salt.

STIR IN any add-ins (nuts, marshmallows, pretzels, etc.).

POUR the fudge into the lined loaf pan. Smooth evenly. Sprinkle extra toppings on the surface if you want. Cover the pan with plastic wrap or more foil.

REFRIGERATE for 2 hours or until the fudge has set.

LIFT the fudge from the pan by holding onto the ends of the aluminum foil. Invert the fudge onto a cutting board.

CUT the fudge into 1-inch squares and serve.

STORE the leftover homemade fudge in an airtight container at cool room temperature or in the refrigerator.