Take the puff pastry out of the refrigerator and let it rest for about 10 minutes. Grease the muffin baking tray (12 troughs). Unroll the dough and roll out to approx. 26 x 45 cm. Cut out 10 circles (each approx. 10 cm Ø).
Place the dough on a floured work surface (do not knead!), roll out again and cut out 2 more circles. Line hollows with the dough circles, press lightly and chill.
Score the vanilla pod lengthwise and scrape out the pulp with the tip of a knife. Bring 1 teaspoon butter, milk, cinnamon stick, vanilla pulp and vanilla pod to the boil in a saucepan and leave to stand for about 5 minutes. Remove vanilla pod and cinnamon stick.
Sift 2 tablespoons of flour. Mix with 250 g sugar and 1 pinch of salt. Stir vigorously into the hot milk. Boil up again while stirring. Let the cream cool down for about 5 minutes. Then stir egg and egg yolk into the cream.
Preheat oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer). Spread the cream into the dough troughs. Add fruit as desired. Bake in a hot oven for 12-14 minutes.
Let the tartlets cool down for about 10 minutes and then remove them from the troughs. Sprinkle each with just under 1⁄2 tsp. brown sugar. Caramelize lightly with a kitchen gas burner or under the grill of the oven.