Preheat your oven to 350° F.

In a medium pot or skillet melt the butter over medium heat, swirling frequently. It will go through a few different phases. First it will melt, then it will bubble and form an opaque foam. The foam will subside and the butter will more or less become clear. Then the butter will bubble up furiously (big soapy bubbles). Once those bubbles begin to subside the butter will start to smell nutty take on a darker color. Butter goes from brown and beautiful to burned pretty quickly, so keep a close eye on it, swirling it constantly. When the darkest parts (it won’t all be perfectly uniform) resemble the color of a nicely aged bourbon, pour the butter into a small glass bowl or measuring cup, making sure to scrape the brown bits from the bottom of the pot/pan. Set aside to cool (I usually chuck it in the freezer for 10 minutes).

Grease a 9 x 13 pan with non-stick spray and line with parchment or aluminum foil so it hangs over two of the sides making a sling (this will help you remove the blondies from the pan later).

In a stand mixer, or using a hand mixer, combine the eggs and brown sugar. Mix at medium-high speed for 2-3 minutes, or until the mixture changes from dark brown and syrupy to light brown and fluffy.

Add vanilla, espresso powder, coffee, and the cooled brown butter. Mix to thoroughly combine.

Mix in both the flours, baking powder, and salt on low speed until almost no dry flour remains.

Sprinkle in half the chocolate chips and finish mixing by hand with a spatula.

Pour batter into your prepared pan and use a spatula to push it evenly to the edges and sprinkle the remaining chocolate chips over the top.

Bake for 20 – 24 minutes, or until the top turns slightly shiny. I would err on the side of under-baking personally as I prefer a fudgier texture.

Let cool in the pan for at least an hour. Remove using the parchment sling, cut into bars and serve.