1. Make a starter: mix together 1/2 cup warm water, 1/2 cup all-purpose flour, one teaspoon sugar and 1/2 teaspoon yeast. Cover and let rest for 20-30 minutes.
2. Add 1/4 cup of water to the starter, rest of flour, salt and olive oil. Mix together thoroughly with a wooden spoon. Transfer on a well floured surface and knead for about 10 minutes dusting with flour as needed until dough is elastic and no longer sticky. Put the dough in a deep glass or plastic dish greased with olive oil. Cover and let the dough rise for about one hour until it doubles in volume.
3. Meanwhile, chop sausage into small pieces and cook in a skillet over medium high heat for about 5-7 minutes until browned. Toast pine nuts and set aside.
4. Put pizza stone in the top oven rack, set the oven on broiler setting and preheat the oven for about 20 minutes.
5. Punch down the dough and roll it out on a lightly floured surface to 1/3 inch thickness, thinner in the middle and thicker on the outer edges. Flute the edges slightly. Drizzle the crust with olive oil, then spread the pasta sauce all around the crust, top with sausage, arugula leaves and two cheeses. Sprinkle with salt and pepper. Put pizza on a foil paper lightly greased with olive oil and dusted with breadcrumbs. Transfer on a hot baking stone. Bake for 2 minutes on broiler setting, turn the heat down to 500F and bake for 5-7 more minutes until crust becomes lightly charred and golden brown. Remove from oven and sprinkle with toasted pine nuts. Cool slightly on a rack before slicing.