Now, for the filling. Using a small spoon, I carefully fill each indentation with jam, being careful not to overfill. Less is more here; a heaped 1/4 teaspoon is usually perfect. If you overfill, the jam will bubble over and caramelize on the pan (which is tasty but messy). I bake one sheet at a time in the center of a 350°F (175°C) oven for 12-15 minutes. They are done when the bottoms and edges are lightly golden, and the jam is just bubbling. The cookies will be very soft. I let them cool on the baking sheet for 5 full minutes before transferring them to a wire rack to cool completely. This allows them to firm up so they don’t break.
Pro Tips for Best Results
I tested the indentation method three different ways: with my thumb before baking, with the end of a wooden spoon before baking, and with the back of a small teaspoon immediately after the cookies came out of the oven. Making the indent before baking is the only reliable method. The post-bake method causes the hot cookies to crumble. Using a rounded tool like a spoon handle gives a more uniform, professional-looking well than a thumb. Trust me, this one works better.
To prevent the thumbprint from puffing up and baking shut—a common frustration—make sure your indentation is deep and wide enough. Don’t be shy! Press down almost to the baking sheet. And here’s a secret: after making the indent, I chill the filled cookies on the baking sheet for 10 minutes before they go in the oven. This extra chill sets the butter again, helping the cookies hold their shape and the thumbprint definition.
For the absolute cleanest look and to prevent jam from sliding off, use a thick preserves or a jam you’ve briefly cooked down. If my jam seems runny, I simmer it in a small saucepan for 3-5 minutes to reduce and thicken it slightly, then let it cool before filling the cookies. This ensures a tidy, glossy pool of fruit that sets perfectly as the cookie cools.
Common Mistakes to Avoid
My first big mistake was using jam straight from the fridge. It was too cold and thick to spoon neatly, and I tore the delicate dough trying to force it in. Now, I let my jam sit at room temperature while I make the dough, or I warm it very gently for a few seconds to make it spreadable. This small step makes filling the cookies a breeze, not a battle.(See the next page below to continue…)