Tea Cookies

8 Tbsp unsalted butter (1 stick)
3/4 cup cane sugar
1 large egg yolk, lightly beaten
1 tsp vanilla extract
1 cup sifted all-purpose flour
1 cup blanched almonds. finely ground
extra sugar, for rolling
1 large egg white, lightly beaten
jam, for filling

Cream together butter and sugar. Add egg yolk and vanilla; beat well. Add flour; beat again.
Chill dough for several hours.
Preheat oven to 325 degrees, adjust rack to middle position.
Combine almonds with two Tbsp sugar. Form dough into small balls and dip in beaten egg white, then in almond-sugar mixture. Press center of each ball with your thumb.
Bake for 5 min, then remove and push down centers again. Bake for another 15 min or until golden brown.
Cool slightly on wire racks and fill centers with jam.

(Recipe source: Martha Stewart)