01 - Combine blueberries, sugar, water, and lemon juice in a small saucepan. Simmer over medium heat, stirring gently until berries burst and syrup thickens, about 8 to 10 minutes. For thicker syrup, dissolve cornstarch in 1 teaspoon water, stir into syrup, and cook 1 to 2 more minutes. Remove from heat and keep warm.
02 - In a large bowl, whisk ricotta, egg yolks, milk, lemon zest, lemon juice, vanilla, 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 clean bowl, beat egg whites until soft peaks form, then gently fold into batter until just incorporated.
03 - Heat a nonstick skillet or griddle over medium heat and brush lightly with butter. Pour 1/4 cup batter per pancake onto skillet. Cook until bubbles form and edges set, about 2 to 3 minutes. Flip and cook another 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.