Preheat oven to 350 degrees F.
Over a double boiler, whisk 3 egg yolks and sugar to a thick, ribbon-like texture. In a separate pot, combine the heavy cream and split vanilla bean, and bring to a boil. Temper the egg yolk mixture into the cream, by whisking a little of the hot cream into the eggs, while constantly whisking, and then whisk the yolk mixture back into the hot cream. Return to the heat and, while whisking continually, finish cooking to a custard stage, approximately 1 or 2 minutes.
For the second part of the creme brulee, whisk the remaining 3 egg yolks for 1 minute. Add the condensed milk and whisk for another minute. Add the key lime juice gradually and whisk for 1 minute. Combine the creme brulee filling with the key lime filling and chill in the refrigerator until needed.
To make the crust, roll out a sheet of puff pastry very thin, 20 by 10-inches. Cut 6 (4-inch diameter) circles out of the puff pastry to line 6 (3-inch) tart pans. Let the dough rest for 30 minutes in the refrigerator. Line the pastry rings with the pastry dough and trim the excess dough flush to the edge of the ring. Place a piece of parchment paper on each tart shell and fill with beans and bake until golden, about 10 minutes. The shells should be very thin and even.
To assemble, fill the shells with the key lime filling and level the tops with a spatula. Dust the tops of the desserts with sugar and using a torch caramelize the tops. Place the desserts on a plate and serve with fruit puree, if desired.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy Shannon Jordinson, Four Seasons Hotel, Palm Beach, FL