Preheat oven to 350° F. Butter a 9x13 baking pan, set aside.
In a large bowl using a hand mixer or in a stand mixer, combine the cake mix, butter, egg and Amaretto. Add the condensed milk slowly and mix until combined. Next, using a rubber spatula, stir 1/4 cup of the sprinkles and all the white chocolate chips.
Pour the batter into prepared baking pan, sprinkle remaining sprinkles on top, and bake for 25 to 30 minutes or until edges are just turning brown.
Allow to cool for at least 30 minutes so the center sets before cutting into squares.
Notes
Blondies remain fresh up to 10 days stored covered at room temperature or in the refrigerator. If you wish to make nonalcoholic birthday bars, simply replace the Amaretto liquor with low-fat milk.