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Frosted Hazelnut maple sugar cookie bars, one with a bite taken.

High Altitude Hazelnut Maple Sugar Cookie Bars

Heather Smoke
Soft and moist maple sugar cookie bars, with brown butter maple hazelnut frosting.

All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet.

5 from 5 votes
Prep Time 15 mins
Cook Time 20 mins
Total Time 35 mins
Course Dessert
Cuisine American


  • Electric Mixer (Stand or Hand-Held)


Cookie Bars

  • 1 cup unsalted butter, softened to room temperature
  • 1 ⅓ cups granulated sugar
  • 2 large eggs, room temperature
  • 1 tbsp vanilla extract
  • 1 tsp maple extract
  • 2 ½ cups all-purpose flour, spooned and leveled
  • 1 ¼ tsp baking powder
  • 1 tsp coarse Kosher salt (if using table salt, use half the amount)
  • ½ cup hazelnuts, roughly chopped


  • 1 cup unsalted butter, browned and cooled to a room temperature solid
  • 1 ½ cups powdered sugar
  • ¼ tsp coarse Kosher salt (if using table salt, use half the amount)
  • 2 tsp vanilla extract
  • 1 tsp maple extract
  • cup hazelnuts, finely chopped


Cookie Bars

  • Preheat the oven to 350F.
    Line a 9x13 baking pan with a piece of parchment/baking paper and snip the corners so the paper fits down into the pan. Alternatively, you can use aluminum foil, and spray the foil thoroughly with non-stick spray.
  • In the bowl of your stand mixer fitted with the paddle attachment (or using a bowl and hand-held electric mixer), beat the softened butter and sugar until light and fluffy, about 3 minutes.
  • Add the vanilla and maple extracts, and mix in the eggs, one at a time, just until combined.
  • In a separate bowl, whisk together the flour, baking powder and salt. Add the dry ingredients and the chopped hazelnuts, and mix the dough on low, just until moistened. The dough will be very thick.
  • Pile the dough into the prepared pan. Since the dough is so thick and sticky, it can be a little tricky to spread it out. The best way is to butter your hands or a spatula and just push the dough out to the edges of the pan as evenly as you can.
  • Bake the cookie bars on the center oven rack for about 20-22 minutes, just until the edges are set and every so slightly browned, but the center still looks a little underdone. Be careful not to over-bake these bars, or they will end up dry. They will continue to bake and set in the hot pan after you take them out of the oven. It's normal for the center of the bars to settle and sink down a little as it cools.
  • Set the pan on a cooling rack and cool completely before frosting.


  • To make the browned butter, melt the butter in a saucepan over medium heat. Continue to cook the butter for several minutes, swirling the pan occasionally, until nutty golden brown solids form at the bottom of the pan. Immediately remove from the heat and scrape the browned butter into a bowl. Let cool completely at room temperature, until the butter returns to a solid.
  • Beat the cooled brown butter with an electric mixer for 1 minute until smooth.
  • Add the powdered sugar, salt, vanilla and maple extracts. Beat for several minutes until very light and fluffy. Fold in the chopped hazelnuts (reserving a few tablespoons to sprinkle on top).
  • Lift the cooled bars out of the pan by the paper, peel the paper off, and set the bars on a cutting board.
  • Spread the frosting over the bars, sprinkle with rest of the chopped hazelnuts, and cut into bars.


Leftover sugar cookie bars should be stored in an airtight container at room temperature for up to 3 days, or wrapped well and frozen for 3-6 months.
The baking pan I used in the photos for today's post is slightly smaller than a 9x13 pan, measuring 8 1/2 x 11 inches.  Since the bars were slightly thicker, I baked them for exactly 25 minutes.
Keyword Brown Butter, Cookie Bars, Hazelnut, Maple, Sugar Cookies
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