Dissolve the yeast in the water, add the sugar, and allow to sit until creamy, about 5 minutes. Beat in the egg and olive oil. Combine the flour and salt, and stir into the yeast mixture. Work the dough until it comes together in a coherent mass, adding flour as necessary. Turn out onto a lightly floured surface and knead for a few minutes, adding flour as necessary, until the dough is smooth; do not overwork. Shape into a ball. Place in a lightly oiled bowl, cover tightly with plastic wrap, and allow the dough to rise in a draft-free spot until doubled, about 1 hour.
Turn the dough out onto a lightly floured surface, gently knead a couple of times. For a galette, use all of the dough in one piece, for a double pie crust, cut into two pieces. Shape each piece into a ball and cover the dough loosely with plastic wrap. Let sit for 5 minutes. Then roll out into thin rounds, as directed in the recipe or use to line oiled pans. If not using right away, freeze the dough to prevent it from rising and becoming too bready. The dough can be transferred directly from the freezer to the oven.