In a large bowl, whisk the flour, salt, and sugar together. Add the cubed butter and, using your fingertips, lightly rub the butter into the flour until it resembles large breadcrumbs with some pieces the size of small peas. You can also use a pastry blender for this job.
Make a well in the middle of the flour mixture and add the egg. Using a wooden spoon, mix the egg into the flour until they’re completely combined.
Add the cream and mix until the dough is firm enough to form a ball when you press the mixture together with your fingers—it may be a little crumbly but do your best to form the dough into a disk and wrap it tightly in plastic wrap. Refrigerate the dough for at least 1 hour and up to 3 days. (You can instead freeze the dough, tightly wrapped in plastic, for up to 3 months. Thaw it overnight in the fridge before you roll and bake.)
Remove the disk of dough from the fridge and let it sit for a few minutes so it’s easier to work with. Divvy the dough in half.
Lightly flour a large sheet of parchment and then place a piece of dough on the parchment. Sprinkle it lightly with flour and place a second sheet of parchment paper on top.
Roll the dough between the 2 sheets of parchment paper to athickness of 1/6 inch (4 mm). If the dough is soft, you might need to put it back in the fridge to firm up a little before you cut it.