• Preheat oven to 450°.
• Finely chop walnuts and thyme. Set aside.
• On a lightly floured surface, unfold pie dough. Sprinkle 1 tablespoon walnuts and 1 teaspoon thyme evenly over each sheet of pie dough. Fold each sheet in half, then in half again. Roll dough into a 10-inch-diameter circle, and cut 4 (4½-inch) circles from each sheet for a total of 8 circles.
• Press each circle into an individual tart pan. Prick dough with a fork.
• Bake until slightly brown, approximately 10 minutes. (If crusts puff during baking, prick again.) Set aside on wire racks to cool.
• In a medium mixing bowl, combine goat cheese, cream cheese, 1 tablespoon sugar, honey, cardamom, and salt. Stir well by hand until all ingredients are incorporated.
• While tart shells are still in pans, divide cheese mixture among cooled shells, spreading evenly. Cover, and refrigerate until cold.
• Cut grapes in half lengthwise. Dip cut surface in remaining ¼ cup sugar. Place cut side up on a baking sheet or broiler pan. Using a culinary torch, caramelize sugar on grapes*. Cool until safe to handle.
• Place 5 grape halves cut side up on surface of each tart to form a flower design.
• Garnish each tart with 3 short sprigs of fresh thyme in center of grapes, and sprinkle tart with orange zest, if desired.

 
*If a culinary torch is not available, broil grapes in oven on highest setting until sugar is caramelized, watching to prevent burning.