Wine Jelly Thumbprint Cookies

1. Preheat oven to 350 degrees F.
2. Line two cookie sheets with parchment paper or a silicone baking mat; set aside.
3. Cream together the butter, shortening and brown sugar with an electric mixer at medium speed for 2 minutes or until fluffy. Scrape down sides of bowl.
4. Add the egg yolks, milk, vanilla and salt, and beat until well combined. Reduce the mixture speed to low and gradually add the flour, mixing until well blended.
5. Measure about 2 teaspoons dough for each cookie and roll into balls. Place the granulated sugar in a small bowl and roll the balls of dough in the sugar to coat.
6. Using the back of a teaspoon or your thumb, make a deep rounded indentation in the top of each cookie.
7. Bake for 10 minutes, then remove from oven. (At this point there may be a little bit of melted butter underneath the cookies, but when they finish cooking it will be all absorbed, and they were perfect!) 
8. It may be necessary to create the indentation once again with a spoon.  
9. Place about 1 teaspoon jam, jelly or preserves into the indentation of each cookie.
10. Bake an additional 5 to 10 minutes, or until lightly browned. Remove from oven.  Cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.

Note: The cookies can be stored at room temperature for up to 1 week, or frozen for up to 1 month.