You'll start a happy conversation when you give these cookies to your valentine.
Stir together flour, sugar, cardamom, and salt. Cut in butter with a pastry blender until dough has the consistency of cornmeal. Add vanilla and zest, and stir until dough forms a ball.
Divide dough in half. Roll each half between sheets of waxed paper into a circle 1/8 inch thick. Chill circles for about 2 hours, or until firm.
Preheat oven to 325 degrees F. Peel off top sheet of paper from one dough circle and cut out cookies using a 2-inch heart-shaped cutter. Place 1/2 inch apart on baking sheets lined with baking parchment. Bake cookies for 15 to 20 minutes, or until pale brown on bottoms. Cool on wire racks. Repeat for remaining dough.
To "glue" a piece of candy onto each cookie, simmer jam in a small pan to thicken, stirring occasionally. Let cool until warm to touch. Spoon a tiny dot onto upper-right portion of each cookie, and gently press a candy conversation heart on top. (You should not see jam.)