Galettes are free form pies that are made without a pie pan and with only a single sheet of pastry. The filling is placed in the middle of a pastry disk and the sides are folded inwards an inch or two around the filling, creating an edge.
One thing to watch with galettes is the amount of liquid in the filling. Since there isn’t really a steep edge to hold in the juices released during baking, if the filling is too wet it can seep out and make the pastry soggy. One solution is to use a thickener, such as cornstarch, just as you would a regular pie. Another option is to drain the filling before baking and reserve the juices for another purpose (such as a sauce for the pie), and just put the fruit in the pie. A third option is to line inside of the pastry with some white cake crumbs that will absorb the moisture released when it bakes.
