Step 1 Sift the flour into a mound on a work surface and make a wide well in the center. Pound the butter with a rolling pin to soften it. Add the butter to the well with the salt, egg yolk and cream. Work these ingredients with the fingertips of one hand until thoroughly mixed. Using a pastry scraper or metal spatula, draw in flour from the sides and work the dough with the fingers of both hands until coarse crumbs form; they should be soft but not sticky. If they seem dry, sprinkle with an additional tablespoon of cream and continue working to form a rough dough. Press the dough together to form 2 balls, one twice as large as the other.
Step 2 On a lightly floured surface, quickly knead the dough. Take a ball of dough and push it away from you with the palm of your hand, flattening it on the work surface. Gather up the dough, and repeat the action two or three times -- this distributes butter in the flour so dough becomes smooth and pliable. Shape it into a ball and cover loosely with plastic wrap. Repeat with remaining dough. Refrigerate the dough for 30 minutes.