Combine butter, and granulated sugar in a mixer bowl. Beat together until light and fluffy.
Add the eggs and vanilla. Beat until just combined.
Slowly stir in the flour, baking soda, cream of tartar, and salt - mixing until just incorporated.
Fold in the white chocolate chips and then the sprinkles.
Divide the dough into 4 equal portions.
Place the dough into separate bowls. Add several drops of food color - one for each bowl of dough. Fold in until incorporated and the dough has achieved the shade you desire. Keep in mind that the color will intensify over time.
Shape each color of the cookie dough into a long log - approx 15” long.
Place each dough next to each other on a large piece of plastic wrap.
Wrap the dough tightly, pressing the ropes together to form a large colorful log.
Chill for at least 30-60 minutes for the dough to firm up. This is important because the food coloring will make the dough quite soft.
Preheat the oven to 350 degrees
Remove the plastic and break off portions of dough and roll it between your hands to form a ball. (about 2 tbsp in size)
Place the dough on a parchment-lined baking sheet and bake for approx 9-11 minutes. Or until the edges are set. Don’t over-bake.
Remove from the oven and top with additional white chocolate chips.
Allow to cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.