Step 1

Line 9-inch square pan with foil, with ends of foil extending over 2 of the sides. Spray foil and sides of pan with cooking spray and rub to cover evenly with a paper towel. Set aside. Also spray a small thin-bladed knife with cooking spray (a butter knife works well for this). Set aside.

Step 2

Combine sugar, butter and half and half in a saucepan (at least 3 quart-size) over medium heat until mixture comes to a full rolling boil, stirring constantly (don't mistake bubbling at the edges for a full boil). Once it comes to a full boil, cook for exactly 4 minutes, stirring constantly. Remove from heat. Add white chocolate chips, marshmallow creme and lemon zest. Stir again until smooth and well mixed (this will take several minutes, don't give up.)

Step 3

Remove 1/4 of the mixture to a small microwave-safe bowl. Remove another 1/4 to another microwave-safe bowl. Add one or two drops of food color (your choice of colors) to each small bowl (I used two drops - one bowl I used a drop each of blue and green to create turquoise and in the other bowl I used a drop of yellow and a drop of green to create a spring green color). Stir both bowls until well mixed. Do not add color to the remaining mixture in the saucepan.

Step 4

Pour approximately half of the plain mixture into prepared pan.  Add about half of each of the colored mixtures in random spoonfuls over the surface. Then add the remaining uncolored fudge batter. Now add the rest of the colored batter, again in random spoonfuls. It's fine to leave areas of white showing. If any of batters start to thicken you can pop them in the microwave for 10-15 seconds to loosen them up.

Step 5

Using the thin edge of the prepared knife, run it back and forth a few times through fudge creating a swirled pattern. Once you get a pretty swirly pattern, stop. If you swirl too much the whole mixture will run together into one overall color.

Step 6

Quickly sprinkle the top with jimmies, sprinkles, nonpareils, etc. I like to sprinkle them in little clusters, sort of like flowers would grow, rather than an even sprinkle all over the surface.

Step 7

Cool completely and then cut into squares. I find the fudge cuts better if I don't refrigerate it, just let it cool for a few hours at room temperature. Use the foil handles to lift fudge from pan before cutting into squares.