Place the puff pastry slices next to each other and defrost on the floured work surface for about 15 minutes. Cut out 18 stars with a cookie cutter (approx. 4.5 cm Ø). Place on a baking tray lined with baking paper.
Mix egg yolk with 1 tablespoon of water. Brush stars with it. Sprinkle with poppy seeds. Slide the tray onto the middle rail of the preheated oven (electric oven: 200 °C/ circulating air: 175 °C/ gas: see manufacturer).
Push a second baking tray tightly over it. Bake the stars for about 18 minutes until golden brown, remove them and let them cool down on a cake rack.
In the meantime peel and wash the radish and slice off 18 thin slices. Use a cookie cutter (4.5 cm Ø) to cut out 18 stars from the radish slices. Use the rest of the radish for other purposes.
Cut the puff pastry stars in half horizontally. Cover a star underside with a slice of radish and spread with 1 tsp. tarama. Spread 1/2 tsp caviar on top. Place the top side of the star on top. Do the same with the remaining stars.