Using a stand mixer, combine the bread flour, all-purpose flour, salt, sugar and butter. Mix on medium as you slowly add a steady stream of ice water until you reach a nice stiff texture. You may need more or less ice water depending on the dough. Once the dough is smooth, wrap the dough in plastic wrap and flatten. Refrigerate for at least a half an hour.
Roll out the dough on a lightly floured surface to about ?-inch thick. Carefully lay the dough over your baking pan pressing down the dough to line the pan. Trim away any excess dough and prick the dough with a fork. Refrigerate for another half an hour.
Preheat the oven to 400°F. Toss the thinly sliced beets with the truffle oil and season with salt and pepper. Lay the beets on a baking sheet and roast just until soft, about 8 minutes. Set aside.
Reduce the oven to 350°F. Using a food processer blend the ricotta, egg yolks, flour, butter, lemon zest and spices until thoroughly mixed but not whipped. Set aside.
Bake the pastry dough in the oven for about 10 minutes on the middle rack; then pour in the ricotta filling and top it with the beets. Roast the tart for another 20 minutes or until the pastry is a nice golden brown and the beets are tender. Transfer the tart to a cooling rack.
Heat the vegetable oil in a skillet over a medium to high flame. Lightly dip each sage leaf in the flour, shaking off any excess. Once the oil begins to ripple, turn down the flame to medium and drop in 5 or 6 sage leaves at a time. Allow the leaves to fry for only 8 to 10 seconds and transfer them to a towel lined plate. Give a light dusting of sea salt and garnish the tarts with the sage leaves.