Place the cream cheese and panela or farmer cheese in a bowl and mix well with a spoon.
Line a baking sheet with parchment paper. Place l of the puff pastry circles on the baking sheet. Brush a 1-inch rim around the outside edge with some of the beaten egg. Pat the cheese mixture into an 8-inch circle in the center and spread the guava paste or jam evenly over the top.
Fold the remaining piece of puff pastry in half and place over the first piece. Unfold the pastry to enclose the filling, being careful not to trap air beneath. Gently press the top and bottom edges together and refrigerate about 25 minutes, or until the dough is thoroughly chilled.
Remove from the refrigerator. Working about 1 1/2-inches from the outside, firmly press the edges of pastry together with the tines of a fork to seal. Then trim the excess dough, leaving an even 1-inch border of crust surrounding the filling. With a sharp paring knife, cut out and discard a 1/4-inch circle of dough from the center, and press out any trapped air. Then, making shallow cuts, trace 6 to 8 circular lines in a spiral pattern from the center hole to the inside edge of the sealed crust (if the dough gets too warm to work with, just return to the refrigerator for 30 minutes or so to harden).
Mix the heavy cream, with the remaining beaten egg and brush over the top of the tart: Cover with plastic wrap and chill at least 2 hours or overnight.
To bake, preheat the oven to 450 degrees. Transfer the pan from refrigerator to the oven and bake 15 minutes, or until puffed and golden brown on top. Reduce the oven temperature to 350 degrees. Bake until the jelly is bubbling and the bottom crust, when lifted with a spatula, is browned, 30 to 40 minutes. Set aside to cool on a rack to 15 minutes. Serve warm.
c.1997, M.S. Milliken & S. Feniger, all rights reserved