Cream together 1 cup of unsalted butter and 2 cups of powdered sugar until light and fluffy, about 2 minutes.

Add in 2 eggs and 2 tablespoons of milk, mixing until just combined.

Gradually incorporate 4 cups of all-purpose flour and 1 teaspoon of salt into the wet mixture.

Divide the dough into three parts, color one with purple gel, the second with black, and leave the last uncolored.

Roll out each colored dough into rectangles, stack and roll tightly into a log, then wrap and chill for at least 1 hour.

Preheat oven to 375°F (190°C) and line a cookie sheet with parchment paper.

Slice the chilled dough into 1/4-inch thick pieces and arrange on the prepared sheet, sprinkle with extra sprinkles.

Bake for about 10 minutes until the edges are lightly golden, then cool on the baking sheet for 10 minutes.