Preheat oven to 350F. Grease 2 12-count (so 24 total) mini muffin tins and set aside.

In a small bowl, combine chia seeds and water. Stir to combine. Let sit for about 5 minutes, until it thickens and is gel-like. Set aside.

In a large bowl, cream together butter and sugars with a hand mixer until light and fluffy.

Add chia mixture and vanilla and stir to combine.

Then add salt, baking powder, baking soda, and gluten-free flour blend. Stir until dough forms.

Spoon dough into the muffin wells. With wet fingers, make a slight hole in the center of each muffin cup, pushing the dough to the sides of the muffin well.

Bake at 350F for 12-15 min, until golden brown and cooked through. Let cool completely.

In the meantime, to make the buttercream, cream the dairy-free butter in a stand mixer fitted with the paddle attachment. Add the vanilla. Then add the powdered sugar 1 cup at a time and let mix until the buttercream is smooth. If you buttercream is too thick, feel free to add a tablespoon of non-dairy milk to thin it out a little bit.

Once the cookie cups are cooled, pipe the buttercream onto each cookie cup. Top with one blueberry and one raspberry each. Serve immediately. Keep in an airtight container or in the refrigerator for best results.