For an easy thumbprint cookie flavor variation try ube. With almond flour and ube extract, these cookies have a short, crumbly texture and vibrant purple hue.
Preheat oven to 350 degrees F and line two baking sheets with parchment paper or a silicone mat.
With an electric mixer or stand mixer fitted with a paddle attachment, cream butter with sugar and salt in a large mixing bowl until light and fluffy.
Add egg yolk and extract and beat until homogenous.
Add all purpose flour and almond flour and gently mix until mixture comes together in a dough.
Use a two tbsp cookie scoop or other spoon to roll small cookie dough balls and place on your prepared baking sheets.
Gently press the back of a 1/2 teaspoon measuring spoon to create small craters in the middle of each cookie.
Scoop a rounded 1/4 teaspoon of ube halaya into each crater.
Chill cookies in the fridge for 20 minutes.
Bake for 10-12 minutes, or until bottom of the cookie becomes lightly browned. Because of the halaya, I keep these cookies in an airtight container in the fridge if not being eaten the day of baking. Allow cookies to come to room temperature before eating.
Notes
If doubling this recipe, you can use one whole egg instead of two egg yolks.
You can substitute more all purpose flour for the almond flour if you wish. Almond flour gives the dough a more crumbly texture and prevents spreading.