1. Make the Jam:

1. In a small pot, combine cranberries, raspberries, apple juice, and brown sugar.
2. Cook on medium heat for 25-30 minutes, stirring occasionally, until the mixture thickens.
3. Let the jam cool in the fridge.

2. Make the Cookie Dough:

1. In a bowl, mix flour, cornstarch, and salt. Set aside.
2. In a mixing bowl, beat butter and granulated sugar until light and fluffy.
3. Add the egg and vanilla extract, mixing until just combined.
4. Gradually add the dry ingredients, mixing until a dough forms.
5. Divide the dough in half, wrap in plastic, and flatten into discs. Chill for 30 minutes.

3. Roll and Cut Cookies:

1. Roll each disc between parchment paper to ¼ inch thick. Freeze for 15 minutes.
2. Cut out cookies using a 2 ½ inch round cutter. Use a smaller cutter for half of them to create centers.
3. Place on a parchment-lined baking sheet and freeze for 1 hour.

4. Bake:

1. Preheat the oven to 350°F (180°C).
2. Bake cookies for 10-12 minutes until the edges are light brown.
3. Let cool, then dust the tops of the cut-out cookies with powdered sugar.

5. Assemble:

1. Spread about 1 teaspoon of jam on the bottom of each solid cookie.
2. Sandwich with a cookie that has a cut-out center.
3. Enjoy your delicious homemade cookies!