Preheat the oven to 350°F. Line an 8x8 square pan with parchment paper.
Prepare the sugar cookie mix as the package directs, add in the white chocolate chips.
Press ⅔ of the prepared sugar cookie mixture in the bottom and about ½” up the sides of the prepared pan. Bake in the preheated oven for 10 minutes. Remove from the oven and let cool for a few minutes.
Spread dulce de leche over the top of the baked sugar cookie bar, then lightly press the remaining dough over the dulce de leche.
Bake for 20-25 minutes, or until the top is golden and the center of the bars have only a slight jiggle to them. Cool completely, then cut them.
