Line an 8x8 inch baking dish with parchment paper, making sure the parchment paper goes up all 4 sides of the baking dish. Set it aside.

Add the butter, half and half and heavy cream to a 3 to 4-quart heavy-bottomed saucepan over medium heat. Stir continuously until the butter is melted.

Add the sugar and keep stirring constantly as the mixture comes to a simmer. This should take between 6-7 minutes. Keep stirring and allow the mixture to simmer for another 3 minutes. Remove from the heat.

Add in the white baking chips. Cover the saucepan and let the mixture rest for 3-4 minutes. Stir until the white baking chips are melted.

Add the marshmallow fluff and stir until completely incorporated.

Stir in the fresh lemon zest, lemon extract. and clear vanilla flavoring into the fudge. Stir just until well combined.

Pour the ¾ of the fudge into the parchment paper-lined baking dish.

Add the yellow food color gel to the remaining fudge left in the saucepan. Stir until tinted fudge is a uniform color.

Drop spoonfuls of the yellow-tinted fudge in dollops over the top of the untinted fudge already in the pan. Use a bamboo skewer, kitchen knife or even a chopstick to swirl and create a marble pattern.

Allow the fudge to sit at room temperature for 30 minutes before covering the baking dish and chilling in the refrigerator for at least 4 hours. Once the fudge is set, lift the fudge out of the pan with the parchment paper. Use a large sharp knife to cut the fudge into 6 slices x 6 slices, giving you 36 pieces of fudge. Keep refrigerated until ready to serve. The fudge will keep for up to 5 days in the refrigerator.

We recommend you use parchment paper (not just cooking spray) for this recipe. You can leave some of the paper hanging over the sides of the pan. This will make it easier to lift the fudge out of the dish once it's set, allowing for easier slicing and serving.

Make sure your spoon continues to stir right to the bottom of the pan. If you begin to feel overcooked milk mixture building up on the bottom of the pan, reduce the heat slightly.

Use your food color sparingly. Each brand of food coloring will yield a different result, so go slowly and add more if needed.