These vegan thumbprint cookies are buttery, soft shortbread cookies with chewy blueberry or apricot jam centers. They are perfectly customizable holiday cookies, so change the filling, glaze them, or sprinkle them with your toppings.
Add all ingredients (rice flour, buckwheat flour, corn starch, sugar, butter, salt, and vanilla extract) to a food processor and pulse until you get a crumble texture.
Take a large bowl and add the dough from the food processor. Knead it with your hands for 2 minutes to form a cookie dough ball. If the ball is dry and crumbles after 2-3 minutes, add 1-3 teaspoons of water, one at a time. The dough should not stick to your fingers. If you add too much water, compensate it with flour.
Scoop 1 Tablespoon of cookie dough and form a small ball with your hands. Place it on parchment paper.
Gently push a ½ teaspoon measuring spoon in the middle to make an indentation for the jam, or use your thumb to make a thumbprint :-). If the cookies crack a bit, don't worry; pat them with your hands. Cracks give them a kind of rustic look anyway.
Add ½ teaspoon of jam in the center of each cookie.
Bake the thumbprint cookies for 10-12 minutes. Baking time may depend on your oven, so check them around 8-10 minutes.
Notes
Measure it with a scale – The most crucial step to ensure your thumbprint cookies turn out perfect is paying attention to measurements. Baking is about precision. Sometimes even minor differences can mess up the results. I always measure the ingredients on a scale and convert the recipe back to cups. I use King Arthur's Weight Chart to ensure that the cup measurements align with the grams. If you want to make perfect cookies every time, measure everything precisely.
Parchment paper instead of silicone mats – I recommend using parchment paper instead of a baking sheet or silicone mat if you make multiple batches. The main reason is that thumbprint cookies right out of the oven are very vulnerable. The jam is also hot and can burn your fingers. Using parchment paper, you can move the cookies to a cooling rack without touching them. Compared to using a baking sheet, you either have to wait or handle them too soon.
Place them close – You can place them relatively close to each other as there is no baking powder, baking soda, or any other type of leavening. Which means they will not rise significantly.
When are they ready? – If they start to brown on the edges, you are too late. Rice flour recipes tend not to get brown much during baking.