Ingredients

• 1/2 cup (1 stick) unsalted butter, at room temperature
• 1/2 cup sugar
• 1 egg yolk
• 1 teaspoon vanilla extract
• 1 1/2 cups all-purpose flour
• 1/2 teaspoon salt
• 1 cup quick-cooking (not instant) oats
• 2 to 3 tablespoons sesame seeds
• 3 to 4 tablespoons apricot, strawberry, or raspberry jam

Instructions

1. Preheat oven to 350 degrees F.
2. Cream butter and sugar on medium speed until light. Beat in egg yolk and vanilla. Whisk flour with salt, then stir into butter-sugar mixture until incorporated. Stir in oats.
3. Pinch off pieces of dough and roll into balls about 1 1/4 inches in diameter. Roll half of each ball in sesame seeds. Place on ungreased cookie sheets, sesame side up, about 1 1/2 inches apart. Bake in the center of the oven for 5 minutes, or until mostly set. With the handle of a wooden spoon or a dowel, press an indentation in the center of each cookie. Return to the oven for another 7 to 8 minutes, until cookies have firmed up and are golden on the bottom.
4. Let cool for a minute on cookie sheets, then remove to wire racks to finish cooling. Not too long before serving, fill the hollow in each cookie with a dab of jam.