Prepare galette dough. In a food processor, combine flour, sugar, salt, and butter. Pulse until butter is in small pieces. Slowly add the water and continue to pulse until a dough forms. Add additional water if needed, 1 tablespoon at a time. Remove dough from food processor and form into a ball. Cover with plastic wrap and chill for 30 minutes.

Preheat oven to 400 degrees F.

Assemble the galette. Remove chilled dough from the refrigerator. Dust clean work counter with flour. Roll doll out into an 11-inch circle. Transfer to a baking sheet. Lay sliced pear in a concentric circle, leaving a 2-inch border. Top with prosciutto and crumbled blue cheese.

Fold over the edges of the dough towards the center to create a border. Chill for 10 minutes.

Brush melted butter on the edges of the galette. Bake for 35-45 minutes or until the edges are golden. Remove from oven and cool on a wire rack for 20 minutes. Slice and serve.