Measure the flour into a large bowl. Add the salt, and stir to mix it in.
Being careful to handle the butter as little as possible (you want to keep it cold, and body heat will warm it up), cut the butter into small pieces, then add to the flour.
Using your hands, work the butter into the flour until the pieces are small (about the size of a pea) and the mixture has a grainy texture.
Add the water (very cold) a little bit at a time, mixing until the dough is all incorporated into a ball. If 1 oz of water doesn’t seem to be enough, you can add a bit more, but add it a little bit at a time, and use the least amount of water possible to hold the dough together.
Flatten the dough into a disc, wrap in plastic and refrigerate for at least 15-20 minutes before working with it further.
Take dough out of the refrigerator, and on a well floured surface, roll dough out to a circle of approximately 12 inch diameter. Transfer to the lined baking sheet.
Spread the crème fraîche evenly in the center of the dough circle, leaving a 2-3 inch border around the edges. Top evenly with the ham and brie slices, and arrange the pears on top. Sprinkle evenly with the thyme leaves.
Fold edges up around the filling. Brush any exposed crust with the beaten egg, then place in the oven and bake until golden brown, about 25-30 minutes. Cool before eating.