Make Blueberry Jam: In a saucepan over medium heat, combine blueberries, sugar, lemon juice, and water. Stir until berries burst and sauce thickens, about 5-7 minutes. Mix in cornstarch slurry and cool.

Brown Butter: Melt butter in a saucepan over medium heat, stirring until golden brown, about 5-8 minutes. Transfer to a glass bowl to cool.

Cream Butter and Sugars: Combine cooled browned butter with granulated and brown sugar in a stand mixer. Beat until light and fluffy, about 3-5 minutes.

Add Eggs and Vanilla: Add eggs and vanilla to the mixture, beating until well combined, about 1-2 minutes.

Combine Dry Ingredients: In a bowl, whisk together flour, baking powder, salt, and cinnamon. Gradually add to the wet ingredients until just combined.

Fold in Blueberries: Gently fold in the prepared blueberry jam and additional blueberries.

Scoop and Chill Dough: Portion dough on a lined baking sheet, make wells for blueberry jam, cover, and chill for at least 30 minutes.

Prepare Streusel: Mix brown sugar, cinnamon, and flour. Cut in cold butter until crumbly.

Bake Cookies: Preheat oven to 350°F (175°C), place chilled dough on baking sheets, sprinkle with streusel, and bake for 15 minutes.