Preheat to 425F and prepare a mini muffin tin (with muffin cups or nonstick spray)
Combine pancake mix and water
Add sour cream to pancake and water mixture. Stir
Fold in frozen blueberries
Add batter to muffin tin, filling almost to the top
Top with streusel mixture
Bake at 425F for 5 minutes. Then, keeping the muffins in the oven, reduce the oven temp to 350F and bake for another 6-8 minutes. Test doneness with a toothpick. You should be able to pull it out clean.
Let cool for a few minutes and enjoy!