From the Samuel Sewall Inn, Brookline, MA
Preheat oven to 350 degrees. Grease cookie sheets.
In a medium bowl, cream together butter and sugar. Add vanilla extract and egg yolk, mixing until fluffy. Stir in flour and chopped almonds.
Measure out dough by the teaspoonful and roll into balls. Make an indentation in each cookie with your thumb, then fill with jam using a teaspoon or pastry bag.
Bake 15 to 20 minutes, until golden brown. Remove cookies from baking sheets to cool.