In a mixing bowl, combine 1 cup of all-purpose flour, 1/2 cup of brown sugar, 1/2 teaspoon of cinnamon, and 1/4 teaspoon of salt. Add 1/4 cup of cold, cubed butter and use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs. Refrigerate the streusel while you prepare the dough.

In a large mixing bowl, beat together 1/2 cup of softened butter, 1/2 cup of brown sugar, and 1/4 cup of granulated sugar until light and fluffy, about 3 minutes. Add in 1 egg and 1 teaspoon of vanilla extract, mixing until well combined and smooth.

In a separate bowl, whisk together 1 1/2 cups of all-purpose flour, 1 teaspoon of baking powder, and 1/4 teaspoon of salt. Gradually add the dry mixture to the wet ingredients, mixing with a spatula until just combined.

Gently fold in 1 cup of fresh blueberries, taking care not to crush them to maintain their shape.

Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper. Scoop out spoonfuls of dough and place them on the baking sheets, dolloping a teaspoon of blueberry jam on each.

Sprinkle the prepared streusel topping over each cookie mound, gently pressing it down.

Bake for about 12-15 minutes until edges are lightly golden and centers look soft.

Allow cookies to cool on the baking sheets for about 5 minutes, then transfer to a wire rack to cool completely.