In a mixer fitted with a paddle attachment, whip butter, sugar and almond extract together until light and fluffy. Turn the mixer to low and slowly mix in the flour.
Cover and refrigerate for one hour.
Remove and form 1" balls, softening somewhat with your hands. Press your index finger to shape one side of the heart and turn 45 degrees the opposite direction to press the other half. Use your thumb to form the pointed end of the heart. The cookie will be round, quick thick with a deep heart impression in the center.
Add jam until it fills the cookie heart. Refrigerate an additional 20-30 minutes.
Preheat the oven to 350F.
Bake the cookies straight from the fridge for 14 minutes or until only lightly browned.
Adapted from Land O' Lakes Thumprint Cookie
Recipe by Just a Smidgen at https://justasmidgen.com/2013/11/08/heart-thimble-cookies/