Chocolate Hazelnut Thumbprint Cookies

Cream the Butter: Add the softened butter and sugar to a large bowl and use a hand mixer or stand mixer to cream them together until light and fluffy, about 2 to 3 minutes. Scrape down the sides of the bowl, then add the thickened flax egg and vanilla extract. Cream together again until incorporated, then scrape down the sides of the bowl one more time.

Dry Ingredients: Place a fine sieve over the bowl and add in the flour, cocoa powder, and cornstarch. Use a spatula to mix the dry ingredients together as you sift them over the butter (they do not have to mix perfectly).

Mix: Use a spatula to combine the dry ingredients; the dough will look very shaggy and dry at first, but should combine into a thick and not very sticky dough. Fold only 1/2 cup of chopped hazelnuts into the dough. (See the recipe notes if you are making this dough ahead of time)

Form the Cookies: Use a 1 1/2 sized tablespoon to scoop out 24 even balls of cookie dough. Use your hands to roll each dough ball into a smooth circle, then place the cookie dough balls evenly on a baking sheet (12 per sheet).

Make the Thumbprint: Fill a small bowl with water. Use a rounded 1 teaspoon measuring spoon to form a “thumbprint” in the center of each cookie, pressing the cookie dough down into a slightly larger circle. I like to lightly dip the measuring spoon in water in between each cookie to prevent sticking.

Coat in Hazelnuts (Optional): Spread the remaining 1/4 cup of chopped hazelnuts across a large plate, so there is a little space between the pieces. Carefully pick up each cookie and lightly press the top of the cookie into the hazelnuts so they stick to the outer edge of the cookie. Return to the baking sheet and repeat with the remaining cookies.

Bake: Bake for 10 to 12 minutes, until the bottom edges of the cookies have set but are not darkened. Place the entire cookie sheet on a wire rack; the cookies will have puffed up some in the oven, so use the same rounded teaspoon to press down on the centers again.

Cool: Let the cookies rest on the baking sheet for 10 minutes to firm up. Add about 1 teaspoon of chocolate hazelnut butter to each cookie, then place half of a hazelnut in the center of the butter.

Serve & Store: Enjoy immediately, or let cool completely before transferring to an airtight container and storing at room temperature for up to 3 days. I would recommend only filling the cookies with hazelnut butter that you plan to eat immediately, as they will stick together if you stack them on top of each other.