Preheat oven to 425°F. Line a cookie sheet with foil and spray with nonstick cooking spray.

Place pastry sheet on a lightly floured surface. With a rolling pin, smooth away Creases. Using a 1-inch square cookie cutter, cut out pieces of puff pastry. Place squares on prepared cookie sheet 1/2 inch apart. Prick the center of each pastry with a fork to prevent puffing up too much while baking.

Bake for 15 minutes, or until lightly browned and slightly puffed. Remove from oven and cool on a wire rack for 10 minutes. Slice each tart in a half lengthwise and set aside.

Slowly heat raspberry jam in a small saucepan, stirring until thinned, about 30 seconds.

Spread 2 teaspoons yogurt on bottom half of each pastry square. Top with a few raspberries, replace the pastry tops, and then drizzle with warm jam. Refrigerate until ready to serve.