Place oven rack in middle position, and place a pizza stone on rack. Preheat oven to 450 degrees. Combine yeast, sugar, and water in the bowl of a standing mixer fitted with the dough hook attachment. Let stand until foamy, about 10 minutes. Stir until yeast and sugar have dissolved. Add 6 tablespoons oil, the chopped rosemary, flour, coarse salt, and Parmesan, and beat on medium speed until dough forms a ball, about 2 minutes.
On a lightly floured surface, knead dough until smooth and elastic. Lightly brush a medium bowl with oil. Place dough in bowl. Cover with a clean kitchen towel, and let rise in a warm place until doubled in size, about 1 hour.
Punch down dough, and turn out onto a lightly floured surface. Cut in half, cover, and let rest for 10 minutes.
On a lightly floured piece of parchment, roll 1 portion of dough into a 9-by-16-inch rectangle, about 1/4 inch thick. Brush with 2 tablespoons oil. Arrange half the Taleggio on top, and sprinkle with 1 teaspoon whole rosemary leaves. Slide parchment and dough onto an inverted baking sheet, and use the sheet to slide parchment and dough onto the preheated stone in oven.
Bake, rotating bread once, until crust is just golden and cheese is bubbling, 10 to 12 minutes. Transfer parchment and bread to a wire rack. Shave half the truffle over top if desired, and sprinkle with flaked sea salt. Repeat with remaining dough, 2 tablespoons oil, 1 teaspoon rosemary leaves, and Taleggio. Slice into wedges or squares, and serve warm or at room temperature.