Soft, buttery cut-out sugar cookies with a gentle sourdough tang, tender centers and delicately crisp edges. Perfect for decorating, they balance sweetness with subtle fermentation notes.
Preheat oven to 350 F (unless long fermenting).
In a stand mixer with a paddle attachment, cream the butter and granulated sugar for a few minutes until light and fluffy.
Add the eggs one at a time and mix until well incorporated.
Add vanilla and sourdough discard and mix until just combined, scraping down the sides as needed.
In a separate bowl, whisk together the flour, baking soda, and salt.
Add the dry ingredients to the wet ingredients about 1/3 at a time, mixing until just incorporated.
Divide the dough into two discs and wrap with plastic wrap. Refrigerate for at least 1 hour or up to 3 days for long fermentation.
On a lightly floured surface, roll dough to 1/4 inch thickness between two sheets of parchment paper.
Use cookie cutters to cut out shapes and transfer to a parchment-lined baking sheet.
Bake for 8–10 minutes, or until the edges just begin to turn golden.
Allow cookies to cool completely before icing.
To make the royal icing: Add powdered sugar, water, and meringue powder to a stand mixer or large bowl.
Using a whisk attachment (or hand mixer), whip until peaks form.
Adjust consistency as needed: add water 1 teaspoon at a time if too thick, or add powdered sugar 1–2 tablespoons at a time if too thin.
Transfer icing to a piping bag (or zip-top bag with a small corner snipped) and decorate the cooled cookies.