In a medium saucepan, combine diced fresh strawberries and granulated sugar over medium heat. Cook for about 45 minutes, stirring and mashing halfway through, until thick and bubbling. Let cool while you work on the cheesecake filling.

In a mixing bowl, blend cream cheese, granulated sugar, and vanilla extract using an electric mixer until smooth and creamy, with no lumps. Scoop into 18 equal portions and shape into discs. Freeze for at least 1 hour.

In a large mixing bowl, cream together softened butter and granulated sugar until light and fluffy, about 3-4 minutes. Add egg and vanilla, mixing well. In another bowl, whisk together all-purpose flour, baking powder, and salt. Gradually incorporate dry ingredients into the butter mixture until a soft dough forms.

Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper. Divide cookie dough into equal portions, flatten each into a disc about 3 inches wide. Place a spoonful of strawberry jam in the center and top with a frozen cheesecake disc. Fold the edges of dough over to seal.

Flatten the stuffed cookie pockets slightly and place them on the prepared baking sheets, spacing about 2 inches apart. Bake for 11-12 minutes, or until edges are lightly golden. Let cool on baking sheets for 10 minutes before transferring to a wire rack.