These glorious glazed pumpkin donut waffles are a must make for fall: with a fluffy, yeasty waffle base infused with pumpkin and brown butter, dipped in a sweet vanilla cardamom glaze.
To make brown butter, place butter in a saucepan set over medium heat. Butter will melt, then will start to foam and sputter. Continue to heat, stirring occasionally, until foam subsides and butter is no longer sputtering, and the solids that settle on the bottom start to turn golden brown. Remove from heat and set aside to cool to lukewarm.
Place warm milk in a large bowl or the bowl of a stand mixer. Sprinkle yeast evenly over top; let sit for 5 minutes. (If using instant yeast, you can skip this step and just whisk the yeast in with the flour).
Whisk in flour with salt until evenly incorporated. Add pumpkin, maple syrup, vanilla, and lukewarm brown butter; mix to combine and no or very few lumps remain. Press a piece of plastic wrap onto the surface of the batter; loosely cover with another piece and refrigerate for at least 2 hours or overnight.
About an hour before cooking, remove the bowl from the fridge and let it come to room temperature. Prepare and preheat your Belgian waffle iron according to manufacturer’s instructions.
Separate eggs; place yolks in a small bowl; whisk with baking soda. Add to dough mixture and stir until mostly incorporated.
Place egg whites in a large bowl or the bowl of a stand mixer. Beat on medium-high speed until it forms medium-soft peaks. Add half of beaten whites to dough; fold to lighten the mixture. Add remaining egg whites and fold until evenly incorporated and no lumps of egg white remain.
If necessary, lightly spray hot waffle iron with cooking spray. Add about 1 cup of batter to iron (or whatever amount your particular brand recommends to fill, but not overflow). Close iron and cook until golden brown (mine took about 4 to 4½ minutes). Carefully remove from iron and place on a wire rack to cool. Repeat with remaining batter (you should have enough for about 5 to 6 waffles).
While waffles are cooling, prepare glaze. Combine butter and milk in a small saucepan set over medium-low heat (use a pan that is just big enough to fit one of your waffle pieces, then you can dip them right in the same pan and not dirty anymore dishes). Gently cook, stirring occasionally, until butter is melted. Add sifted powdered sugar and stir until sugar is dissolved and no lumps remain. Remove from heat and whisk in vanilla, cardamom, and salt.
Break waffles into quarters (if your waffle iron allows it) as the smaller pieces are easier to dip. Dip one side of waffle into glaze, then lift straight up, allowing any excess glaze to drip back into the pan. Invert and place on cooling rack. Repeat with remaining pieces. Serve freshly dipped waffles at room temperature.
While the waffles are best when they are fresh, if you want to make them ahead of time, you can refrigerate or freeze them unglazed, then bring to room temperature (or toast lightly in the oven to re-crisp the outsides) and then glaze them just before serving.
Notes
*Note that there is no cinnamon or spice in the batter itself. If you decide to add some, be sure to add it in the morning with the egg yolks, as cinnamon (as well as other spices like cloves and allspice) can inhibit yeast development in high quantities.