Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, whole wheat flour, baking powder, salt, and ground cinnamon until well combined.

Add cold unsalted butter into the flour mixture and work until it resembles coarse crumbs, about 2-3 minutes.

Gently stir in brown sugar, milk, and vanilla extract until the dough comes together without over-mixing.

Turn the dough onto a floured surface and knead gently for 1-2 minutes until smooth.

Roll or pat the dough into a rectangle about ½-inch thick.

Score the dough into large squares, about 3 inches each, and optionally press a cross pattern in each square.

Transfer the scored dough to the baking sheet and bake for 20-25 minutes until edges are lightly golden brown.

Let cool slightly on the baking sheet before breaking into squares for serving.