Prepare the Cookie Dough:

1. Cream the Butter and Sugar: In a large bowl, beat the softened butter and powdered sugar together until light and fluffy, about 2-3 minutes.
2. Add Vanilla and Dry Ingredients: Mix in the vanilla extract, then gradually add the flour and salt, mixing until the dough starts to come together. If you’re using cornstarch, add it at this stage to ensure the dough firms up.
3. Chill the Dough: Wrap the dough in plastic wrap and chill in the refrigerator for 30 minutes to firm it up and make it easier to handle.

Add the Raspberry Swirl:

4. Prepare the Jam: If you’re using raspberry jam, heat it gently in a microwave or on the stovetop until it becomes slightly runny and easier to swirl. If using raspberry puree, simply stir it until smooth.
5. Roll Out the Dough: After chilling, roll the dough out on a lightly floured surface to about ¼ inch thick.
6. Add the Raspberry Jam: Drop small spoonfuls of raspberry jam or puree onto the dough and swirl it gently using a toothpick or knife. Be careful not to overmix, as you want the swirl to remain visible.

Shape and Bake the Cookies:

7. Cut the Cookies: Using a cookie cutter, cut the dough into your desired shape—rounds, squares, or even heart-shaped for a festive touch.
8. Chill Again: Place the cut cookies onto a baking sheet lined with parchment paper and refrigerate them for another 10 minutes before baking. This will help them keep their shape while baking.
9. Bake: Preheat your oven to 350°F (175°C) and bake the cookies for 10-12 minutes, or until the edges are lightly golden.
10. Cool: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.