Preheat oven to 350F and line a 9×9-inch pan with parchment paper. 

In a large bowl, mix together cake mix, butter, and egg. The batter will be very thick; keep beating until it goes from pea-sized crumbles to a tacky, thick dough.

In you prepared pan add 1/2 of the strawberry dough pressing it down to form a crust. Evenly sprinkle the white chocolate chips over the dough and drizzle with the sweetened condensed milk. You want about 3/4 of a can or 10 oz. 

Sprinkle the rest of the strawberry dough on the top. Gently pressing down. Top with some additional white chocolate chips if desired. 

Bake for about 27 to 30 minutes or until edges are set and the center is mostly set. Allow pan to cool on a wire rack for at least 1 to 2 hours (overnight is better) or until bars have firmed up enough to cut. Drizzle with some melted white chocolate and sprinkles if desired.