• Preheat the oven to 350 degrees F. Spray a 9×9-inch baking pan liberally with nonstick spray. Set it aside.
• In a large bowl, whisk together the brown butter and sugar until combined. Stir in the vanilla extract, then add the eggs and whisk until a smooth batter forms. Add in the flour, baking powder, soda and salt. Stir until the dry ingredients are incorporated completely. Stir in the chocolate chips.
• Spread the batter in the greased 9×9-inch pan. Prep the streusel.

streusel

• Whisk together the oats, sugar, flour and cinnamon until combined. Stir in the melted butter until the mixture is moistened. Crumble it evenly over top of the blondie batter. Bake the bars for 30 to 35 minutes, or until the center no longer jiggles and the edges are golden. Let cool completely before cutting.