In a medium saucepan over low heat, melt the butter.
Remove from heat and scatter 1 cup white chocolate chips evenly over the butter. DO NOT stir!
Allow chip and butter mixture to sit for about 10 minutes.
Meanwhile, in a large mixing bowl, combine flour, brown sugar, and baking powder.
Add the eggs, vanilla, and white chocolate butter mixture to the flour mixture. Beat until just combined.
Fold in remaining 1 cup white chocolate chips, as well as cinnamon chips.
Spread batter into a greased 9x13-inch pan.
In a small bowl, whisk together granulated sugar and cinnamon.
Sprinkle evenly over batter in the pan. Lightly score the top of the batter with a knife -- just a few swirls to add texture.
Bake at 325 degrees for about 25 minutes, or until edges are golden brown and a toothpick inserted near the center comes out clean.
Remove to a wire rack to cool completely.
Cut into bars.
Store in an airtight container in a cool, dry place for up to a week. These can be frozen for up to 3 months.