1. Fit your food processor with the coarse shredding plate and force the cheese through the feed tube. Remove the shredding plate and insert the metal chopping blade. Add the flour to the work bowl and process 5 seconds to break up the cheese. Slice the butter into pats, add it to the work bowl, and process until the dough gathers in a lump. (To make dough by hand, shred the cheese on the large-hole plate of a box grater and combine it with the flour in a mixing bowl. Cut the butter into 1/4-inch cubes and add. Chop mixture with a wire pastry blender until the cheese and butter are reduced to tiny bits, and then knead the dough until smooth. Wrap tightly in plastic and refrigerate until firm but malleable, like potting clay, 30 minutes to 1 hour.)
2. Set a rack in the lower-middle level of the oven and heat the oven to 350 degrees. Place the dough between 2 sheets of wax paper and roll into a 12-inch circle. Slip the dough onto a rimless 14-17-inch baking sheet and chill 5 minutes. Peel off and discard the top sheet of wax paper, flip the dough onto the sheet, and peel off and discard the other sheet of paper. Bend in the edges of pastry circle 1/4 inch all the way around, then press with a fork. Prick the bottom of the crust at 1-inch intervals with a fork. Bake the crust until pale brown and firm to the center, 17 to 22 minutes. Release the crust by bending the corners of the sheet.
3. Peel the apples, cut into quarters, and remove the cores. Cut the apples in half lengthwise, making eighths, then slice the eighths crosswise at 1/4 inch intervals, making about 4 cups apple dice. In a very large skillet (not cast iron), heat the butter until sizzling over high flame. Add apples and sauté, stirring frequently, until just tender, 4 to 7 minutes. Sprinkle in the sugar and stir until the apples are glazed, and then add the cranberries, cinnamon, and salt. Cook, stirring often, until nearly all the juice has evaporated and the apples are glazed with thick syrup. Remove the skillet from heat and set aside until you assemble the dessert.
4. When you are ready to serve, stir the walnuts into the apple mixture, then spread the filling over the pastry and smooth it with the back of the spoon. Bake the galette in a 375F degree oven until thoroughly heated through, 5 to 10 minutes. Serve at once with vanilla ice cream.
Ahead of Time Notes: The crust may be prepared any time on the day of serving; simply set it aside at room temperature. The topping may be made 3 days ahead. Let it cool to room temperature, then refrigerate in a covered container. Stir in the walnuts just before baking.