01 - Combine blueberries, sugar, lemon juice, lemon zest, and 1 tablespoon water in a small saucepan. Cook over medium heat, stirring occasionally, until blueberries begin to burst, about 3 to 5 minutes.
02 - In a small bowl, mix cornstarch with 1 tablespoon water. Stir into the sauce and simmer for 1 to 2 minutes until thickened. Remove from heat and set aside.
03 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
04 - In another bowl, whisk buttermilk, milk, eggs, melted butter, lemon zest, lemon juice, and vanilla extract until smooth.
05 - Add wet ingredients to dry ingredients and gently stir until just combined; the batter should remain slightly lumpy.
06 - Fold fresh blueberries gently into the batter.
07 - Preheat a nonstick skillet or griddle over medium heat and lightly grease with butter or oil.
08 - Pour 1/4 cup batter per pancake onto the skillet and cook until bubbles form on the surface and edges look set, about 2 to 3 minutes. Flip and cook for an additional 1 to 2 minutes until golden brown.
09 - Continue cooking remaining batter, keeping pancakes warm until all are done.
10 - Stack cooked pancakes and top with warm blueberry sauce and additional fresh blueberries if desired.