Preheat oven to 350 degrees F. Add butter, cream cheese and flour to a food processor. Pulse until a soft ball of dough comes together. Roll 24 even sized balls of dough and place each one in the well of a mini muffin pan. Press out the dough with your fingers or a mini pie tamper dipped in flour to make a mini pie crust.
Add cornstarch and sugar to a small saucepan and whisk until there are no lumps. Add blueberries, water and lemon zest and stir. Bring to a simmer and cook, stirring the whole time, until thickened and the blueberries start to break down, about 5 minutes.
Fill each mini pie crust with filling to the top. You'll have a little filling leftover. Bake for 25 minutes, until bubbly and golden.