Combine dry ingredients: brown rice flour, tapioca starch, blanched almond flour, baking soda, and salt and whisk together. Set aside.
In a large mixing bowl, combine the room temperature butter and almond paste. Beat until well combined (this can be done with a mixer or whisking by hand).
Scrape down the butter from the sides of the bowl and add the sugar; beat well.
Add the egg and almond extract and beat until well mixed. Scrape down the sides of the bowl.
Add the dry ingredients to the butter mixture and use a wooden/mixing spoon to combine until a cohesive cookie dough comes together.
Using a scoop or a spoon, portion out the cookie dough into 20 gram pieces and roll into balls. (Or skip the weighing completely and scoop out dough balls roughly about the same size.)
Cover cookie dough balls with a cloth or plastic wrap until you are ready to bake so they do not dry out.
Place cookie balls on a parchment-lined baking sheet. Flatten each ball slightly with your fingers, the bottom of a drinking glass, or the bottom of a measuring cup.
Top each cookie with a sliced almond.
Beat together the egg and water for the egg wash and brush onto each cookie.
Bake for 20 minutes. Remove promptly because they will start to darken quickly.
Remove baking sheet from oven and let the cookies cool on the pan for 5-10 minutes (this will help them crisp up as they cool). Transfer to a rack to cool completely.
Store in a sealed container for approximately one week.
¾ cup of butter = 168 grams
100 grams of almond paste is approximately ⅓ cup + 2 tablespoons packed
Marzipan is not the same as almond paste and it cannot be used as a substitute in this recipe.
I like to measure out the butter and almond paste while cold and put them in the mixing bowl to let them come to room temperature before beating. It is easier to handle/measure them when they are cold than when they are soft.
Tapioca starch = tapioca flour.
Butter mixture can be creamed/beaten by hand using a wire whisk.
Weighing out the dough to 20 grams each is optional, but it makes for more "perfect" looking cookies!
Lard is used in some almond cookie recipes instead of butter and would make this cookie dairy-free and more crisp. But it will not give as much flavor as the butter.
If you use margarine to replace the butter, be sure the packaging clearly states that the margarine is dairy-free if you are lactose intolerant.
If your oven has uneven hot spots, turn the baking sheet around halfway through baking.
Store cookies in a sealable container or bag for a week.