In large bowl, cream butter and sugar until light and fluffy, 5-7 minutes. Beat in egg. Gradually add flour until blended. Stir in sprinkles. Form dough into a disk; cover and refrigerate 1 hour.
Preheat oven to 375°. Line a baking sheet with parchment. Place dough on parchment and roll into a 12x8-in. rectangle. Score the dough into 24 rectangles. Bake until edges are golden brown, 10-15 minutes. Remove to a cooling rack; cool.
Break or cut along score marks. Dip 1 edge of each cookie into melted chips, then dip in additional sprinkles; place on waxed paper until set.
