Slice the butter into small pieces and place it in the freezer for 5 minutes.
In the bowl of a food processor, process the almonds and 1/4 cup flour to a fine crumb, about 1 minute. Add the remaining flour, the sugar, and salt, mix for 5 seconds.
Add the frozen butter and process for 10 to 15 seconds more or until you can no longer see the larger pieces. If you open the bowl you will feel them as larger granules in the flour mixture.
Pour in the beaten egg and water in a thin stream, with the processor on and mix until the ingredients form a dough and separate from the bowl. You might need to add 1 to 2 teaspoons more of cold water.
Form the dough into a disk, wrap tightly with plastic wrap, and refrigerate for 30 to 45 minutes.
Roll the dough to 1/4-inch thickness for an 8- to 10-inch inch crust and to 1/8- inch thickness for tartlet shells or disks. (This dough is easier to roll between two pieces of plastic wrap.)