01 - Combine blueberries, sugar, water, and lemon juice in a small saucepan. Simmer over medium heat, stirring gently until berries burst and mixture thickens, about 8 to 10 minutes. If a thicker syrup is desired, dissolve cornstarch in 1 teaspoon water, stir into syrup, and cook an additional 1 to 2 minutes. Remove from heat and keep warm.
02 - In a large bowl, whisk together ricotta, egg yolks, milk, lemon zest, lemon juice, vanilla extract, and melted butter until smooth. In another bowl, mix flour, sugar, baking powder, baking soda, and salt. Stir dry ingredients into wet mixture until just combined. In a separate clean bowl, beat egg whites until soft peaks form, then gently fold them into the batter.
03 - Heat a nonstick skillet or griddle over medium heat and lightly brush with butter. Pour 1/4 cup batter per pancake onto skillet. Cook until bubbles form on the surface and edges appear set, about 2 to 3 minutes. Flip and cook an additional 1 to 2 minutes until golden and cooked through. Repeat with remaining batter, adding butter as needed.
04 - Stack pancakes on plates and spoon warm blueberry syrup over the top. Serve immediately.