1. Combine first 5 ingredients and cardamom, if desired, in a heavy saucepan; bring to a boil over medium-high heat. Reduce heat to medium-low; cook 5 minutes. Remove from heat; strain and discard solids. Stir in brandy and nuts.
2. Arrange tart shells on a parchment paper-lined baking sheet. Divide nut mixture evenly among shells. Bake at 350° for 8 to 10 minutes or until pastry is golden. Store, uncovered, at room temperature until ready to serve.