In a large bowl, cream butter, sugar and extract until light and fluffy.
Add half of the flour and mix on low speed of electric mixture.
Add remaining flour and mix on low speed of electric mixer until dough forms a ball.
Cover and refrigerate for 1 hour or until dough is easy to handle.
Roll into 1-inch balls and chill dough again another hour.
Make an indentation in the center of each cookie with your thumb or the bottom of a wooden spoon. (This is easier if you hold each ball in your hand so the cookies don't break apart while inserting the wooden spoon).
Place 1-2 inches apart on lightly greased baking sheets.
Fill indentation in each cookie with raspberry jam.
Bake at 350˚ for 14-18 minutes or until edges are lightly browned.
Remove to wire racks to cool completely.
Spoon additional jam into cookies if desired.