Jam Thumbprint cookies

We recently visited Philadelphia. In Philly, there are all these little bakeries, and they sell boxes of assorted cookies. These are cookies my boyfriend adores. One of the cookie types is a fruit filled thumbprint cookie. I decided to try and recreate those cookies. Well, these cookies are really nothing like the bakery cookies in Philly. The cookie base is to buttery, and I should have used fruit instead of jam. But, they are good in their own right, buttery and sweet. 

Adapted from Cooking During Stolen Moments

1 c. butter, softened
1/2 c. sugar
2 egg yolks
1 t. vanilla
1/2 t. salt
2 c. flour
Raspberry jam, although you can use your preferred flavor

1. Beat butter and sugar together until creamy. Lightly beat the egg yolks and add to the mixing bowl. Add vanilla and salt and mix until combined. Add the flour slowly, mixing with each addition.

2. For each cookie, roll slightly more than a teaspoon of dough into a ball. Place on a baking sheet, make an indentation in the center with you thumb and add a dollop of jam. Repeat until done.

3. Bake at 350 degrees for 10 minutes. Cool on a wire rack.