For the Dough:
1 1/2 cups flour
6oz. cold butter cut into small cubes
pinch of salt
4 1/2 tablespoons ice cold water
For the Filling:
1 sweet potato
1/4 lb Kidchego goats cheese, grated
1 heaping spoonful mustard (Dijon or whole grain)
In a medium bowl, combine the flour, salt, and thyme. Cut the butter into small cubes, and then using a pastry cutter or your fingers mix the butter into the flour until it resembles coarse sand.
Add the water and quickly bring the dough together in to a very rough ball (it’s ok if it’s still falling apart and kind of dry.) Tightly wrap the dough in 2 sheets of cling film and pop in the fridge to rest for at least an hour.
While the dough is resting, peel and thinly slice the sweet potato and beet (use a mandolin if you have or just a sharp knife). Preheat the oven to 350F.
When the dough is rested, roll out into a circle and spread the mustard. Layer the sweet potato and beet slices in circle, alternating for a colorful effect. Sprinkle the grated cheese along the perimeter of the slices (to ensure a cheese crust after baking) and carefully lift and fold the crust up and over the sweets and beets.
Brush the top of the crust with milk or a beaten egg, and season with salt and pepper. Pop in the oven for 45-50 minutes, or until the crust in golden brown and the cheese melted