First Step: Set up your workspace. Grease a 9×13-inch pan and line it with aluminum foil for effortless removal. Chop 1 cup nuts if using, and measure all ingredients precisely. Room-temperature butter blends best. Have a heavy saucepan ready, at least 2-quart size, to handle the boil without overflow. Lay out a wooden spoon or heatproof spatula for stirring. This prep takes 5 minutes and ensures smooth sailing.

Second Step: Combine 3 cups sugar, 3/4 cup butter, and 2/3 cup evaporated milk in the saucepan. Place over medium heat. Stir constantly to dissolve sugar fully. Bring to a full rolling boil, where bubbles cover the surface and cannot be stirred down. Boil exactly 5 minutes, stirring vigorously. Watch the clock; this precise timing is key to no fail fantasy fudge. Medium heat around 350°F prevents scorching. If it bubbles too high, lower slightly.

Third Step: Off heat, add 12 oz semi-sweet chocolate chips first. Stir until fully melted and glossy, about 1 minute. Next, incorporate 7 oz marshmallow creme, beating until no streaks remain. Add 1 tsp vanilla and nuts. Stir briskly for 2-3 minutes. The mix turns from grainy to satin-smooth. Use muscle here; thorough mixing dissolves everything for creamy texture. If stubborn lumps appear, apply gentle heat for 10 seconds.

Fourth Step: Pour the smooth batter into the prepared pan. Spread evenly with spatula. Let cool at room temperature for 1 hour. This prevents sweating later. Refrigerate 3 hours or until firm. Avoid rushing with ice; it shocks the texture.

Final Step: Lift foil to remove fudge. Cut into 1-inch squares with a sharp knife dipped in hot water for clean edges. Yields 48 pieces. Store as directed. Total time: 20 minutes active, 4 hours passive. Perfect for holiday trays or quick treats.