Begin by combining 2 cups of finely diced fresh strawberries with 1 cup of granulated sugar in a medium saucepan. Cook over medium heat for about 45 minutes, carefully mashing the mixture halfway through, until the jam thickens and darkens in color. Once done, remove it from heat and allow it to cool completely.

In a mixing bowl, beat together 8 ounces of softened cream cheese with 1/4 cup of granulated sugar and 1 teaspoon of vanilla extract until the mixture is smooth and creamy. Once blended, divide the filling into 18 equal portions and flatten them into discs. Place the discs on a parchment-lined tray and freeze them for about 2 hours or until solid.

In a large mixing bowl, beat together 1/2 cup of softened unsalted butter and 3/4 cup of granulated sugar until the mixture appears light and fluffy, which should take about 3-4 minutes. Add in 1 large egg and 1 teaspoon of vanilla extract, mixing until the batter is pale and voluminous.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking powder, and a pinch of salt until evenly combined. Gradually fold this dry mixture into the butter mixture, stirring until just incorporated.

Divide the cookie dough into four equal parts, rolling each into a ball. Flatten each ball slightly and place a tablespoon of the thick homemade strawberry jam in the center. Take one of the frozen cheesecake discs and place it on top of the jam, then fold the dough around it, sealing the ends securely.

Preheat your oven to 350°F (175°C) while arranging your stuffed cookies on lined baking sheets. Bake for 11-12 minutes, or until the edges are lightly golden and the tops look firm but still soft. Let the cookies cool on the tray for 10 minutes before transferring them to a wire rack to cool completely.