To make five-minute fudge, combine a 32-ounce bag of powdered sugar with 1 cup of cocoa powder in a large bowl. Stir them together until they are well combined. Heat and melt two sticks of unsalted butter with 1/2 cup of milk, either in a microwave or on a stove.
Stir the hot melted butter and milk into the cocoa powder mixture, making sure it is mixed well and all of the sugar is completely incorporated. Do this step quickly, as the fudge needs to be spread into a pan while it is still warm. Stir 1 1/2 cups of raw walnuts and 2 tablespoons of vanilla extract into the fudge mixture.
Promptly pour the fudge onto a foil-lined baking sheet or casserole dish. Spread the fudge with a knife or spatula to the desired thickness. Leave the fudge at room temperature, and allow it to set. The time fudge takes to set depends upon the temperature; if the house is very warm, put the fudge in the refrigerator for a short time. When the fudge has set, use the foil to transfer it to a cutting board and use a sharp knife to cut it into squares. Serve it immediately, or store it in an airtight container.