Blueberry lemon cookie cups are filled with a blueberry lemon curd inside a soft and chewy lemon sugar cookie cup. These cookies are perfect for summertime tea parties and gatherings!
Add blueberries, zest, and water to medium saucepan and set over medium-high heat.
Bring to boil, then lower to simmer until blueberries soften and burst. Help it along by stirring and mashing berries that are ready. Strain into a bowl with fine mesh sieve, pressing pulp through. Make sure to scrape the outside of the sieve for puree as well. Allow to cool.
In a large bowl, beat butter and sugar until fluffy (2 minutes). Add eggs and egg yolks one at a time, beating until incorporated. On low, mix in lemon juice, blueberry puree, salt, and cornstarch. It will look curdled and weird, but will smooth out once it heats up.
Put mixture back into sauce pan and cook on medium-low heat, stirring constantly until thickened. This will take anywhere between 10-20 minutes.
Remove from the heat and strain into a bowl through fine mesh sieve. Add curd to jars
and let come to room temperature. Cool in refrigerator until ready to fill cookie cups.
Preheat oven to 350°F. Grease a 24-count mini-muffin pan.
In a large bowl, cream together butter and sugar for 4 minutes. Add eggs, vanilla, lemon juice, and zest. Stir to combine.
Stir in flour, baking powder, baking soda, and salt. Mix until just combined.
Fill each of the 24 holes to the top with cookie dough. Press down to level. Bake for 13-15 minutes. Remove from the oven and press a hole in the center of each cookie using a small pestle or other rounded object.
Let sit in muffin tin for at least 5 minutes. Remove from tin and place onto cooling rack. Cool completely.
Using a pastry bag, fill each lemon cookie cup to the top with blueberry lemon curd. Top with blueberries or candied lemon pieces, whichever you prefer. These will keep in the refrigerator for a couple days in an airtight container or you can eat them immediately!