1/2 cup butter, softened
1/4 cup packed brown sugar
1/2 teaspoon vanilla extract
1 cup flour (I use gluten-free pancake mix, and it turns out beautifully)
1/2 cup finely chopped walnuts or pecans
2/3 cup any flavour fruit jam or jelly
1/4 teaspoon salt
Heat oven to 300 degrees F. Grease cookie sheets.
Separate egg, reserving egg white. Cream butter, sugar, egg yolk, and vanilla.
Add flour and salt, mixing well.
Shape dough into 1.5" balls. Roll in egg white, then walnuts. Place on cookie sheets about 2 inches apart. Bake for 5 minutes.
Remove cookies from oven. With thumb, dent each cookie. Put jelly or preserves in each thumbprint. Bake for another 15 minutes.
Cool on rack.
Try not to eat them all. They have a delicate, subtle flavour, and are one of the tastiest cookies I've ever made, and that's saying a lot, because I make damned fine cookies.