With mixer set on low speed slowly add in flour and mix until combined (it will take a while and will appear dry and sandy at first but it will start to come together, if it doesn't you can add a few teaspoons of milk).
Mix and fold in 2 1/2 Tbsp sprinkles. Press dough into an even layer in prepared pan (I did it with my hands first then used the bottom of a flat measuring cup to help smooth it out).
Cool completely then transfer to an airtight container and store at room temperature.
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