Peanut-Butter-Oat Drop Cookies with Jam

Preheat oven to 375°F. Combine butter, brown sugar, peanut butter, baking soda, and salt in a large bowl and beat with an electric mixer on medium-high speed until light and creamy, about 2 minutes.

Beat in egg yolk and vanilla, then add flour and mix until just combined. Scoop dough into 1-inch balls and roll in oats to coat; place cookies on parchment-lined baking sheets, spaced 1 inch apart.

Bake, rotating pans halfway through, until puffed and just set around edges, 10 to 12 minutes. While cookies are still warm, indent centers with the end of a wooden spoon; fill each with 1/2 teaspoon jam. Transfer to a wire rack and let cool completely before serving.