1. Spray a 9-inch pan lightly with cooking spray, then line it with a double thickness of foil. This makes it easier to life it out of the pan later. Extend ends of foil over the sides of pan. Spray lightly again and wipe out any excess spray with a paper towel.
2. Place semi-sweet chocolate chips and food coloring in a heat-safe bowl. Set aside.
3. Place butter in a large microwave-safe bowl. Use a large bowl as mixture will bubble up while cooking. Cover bowl with a paper towel to keep it from spattering. Cook on high for 1 1/2 minutes or until butter is melted.
4. Add sugar and half & half; mix well. Microwave on high power for 3 minutes, stir and cook another 2 minutes. Stir well. If butter seems to separate out just keep stirring til it mixes back in. Scrape down sides of bowl and return to microwave. Microwave 3 more minutes, stir again, then cook another 2 ½ minutes in the microwave
5. Remove from microwave, add marshmallow creme and stir. Add white chocolate chips and vanilla. Stir until very smooth and all ingredients are well incorporated.
6. Immediately transfer about ½ of the hot chocolate mixture to the chocolate mix in other bowl. Stir well with a strong handled spatula until chocolate chips are completely melted and incorporated
7. Working quickly with two clean medium size ice scoops or 2 tablespoons, plop scoops of each mixture in a random pattern into a prepared pan.
8. When complete, lift up pan and drop from about 1 inch above work surface. Repeat several times to remove any air bubbles. Take a knife and run the blade through the fudge to create the swirly effect.
9. Cool completely. Use foil handles to life fudge from pan before cutting into squares.