Preheat the oven to 350°F. Line a 9-inch square baking pan with parchment paper and trim away any long edges. Whisk together the ground flaxseed and 3 tablespoons warm water in a small bowl, then set aside to thicken for about 5 minutes.

Place the melted butter and both sugars in the bowl of a standing mixer fitted with the whisk attachment, then beat together until mixed well, about 1 minute. Add in the flaxseed mixture, maple syrup, and vanilla, then beat for an additional 2 minutes, until the mixture is smooth and glossy.

In a separate bowl, stir together the flour, baking soda, and salt, then add half the dry ingredients to the wet ingredients and mix on low speed until incorporated. Scrape down the sides and bottom of the mixing bowl, then add the rest of the dry ingredients and mix again. Use a rubber spatula to stir in the pecans.

Spread the mixture evenly into the prepared baking pan, then transfer to the oven and bake for 35 to 40 minutes, until golden brown around the edges. When poked with your finger, the finished blondies will feel quite soft and underbaked - this is what you’re looking for, and ensures the blondies will have a soft and chewy texture.

Remove the blondies from the oven and allow them to cool in their pan for 15 minutes. After 15 minutes, use the edges of the parchment to help you lift the blondies (parchment and all) to a cooling rack. Allow to cool completely before cutting and glazing.

When completely cool, make the glaze. Whisk together the powdered sugar, maple syrup, bourbon (if using), and optional maple extract in a medium bowl until smooth. The glaze should be thick but still able to drizzle: if it’s too thick, add an additional teaspoon or two of maple syrup, and if too thin, add an additional tablespoon or two of powdered sugar.

Cut the cooled blondies into bars, separate slightly, and drizzle the cut bars with the glaze, allowing some glaze to run down the sides of the bars. Serve immediately or allow the glaze to harden, then serve.

The glazed blondies will keep at room temperature in a covered container for up to 5 days and can be frozen for up to 3 months. Defrost on a plate at room temperature for about 30 minutes.