Making Raspberry Thumbprint Cookies is a delightful task. Follow these step-by-step instructions:

1. Preheat the Oven: Begin by preheating your oven to 350°F (175°C) and lining a baking sheet with parchment paper.
2. Cream Butter and Sugar: In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
3. Add Egg Yolks and Vanilla: Mix in the egg yolks one at a time, followed by the vanilla extract, until well incorporated.
4. Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour and salt.
5. Mix Dry and Wet Ingredients: Gradually add the flour mixture to the butter mixture, stirring until a soft dough forms.
6. Shape the Cookies: Using your hands, roll the dough into 1-inch balls and place them on the prepared baking sheet, spacing them about 2 inches apart.
7. Create Thumbprints: Use your thumb or the back of a spoon to make an indentation in the center of each cookie.
8. Fill with Jam: Spoon a small amount of raspberry jam into each thumbprint. Make sure not to overfill, as the jam may bubble over during baking.
9. Bake: Place the baking sheet in the preheated oven and bake for 10-12 minutes, or until the edges are lightly golden.
10. Cool: Once baked, remove the cookies from the oven and let them cool on the baking sheet for 5 minutes. Then, transfer them to a wire rack to cool completely.
11. Dust with Powdered Sugar (Optional): For a finishing touch, lightly dust the cooled cookies with powdered sugar before serving.

These simple steps will guide you to create the most delightful Raspberry Thumbprint Cookies, sure to impress everyone who tries them.