In small bowl, mix ricotta cheese, chopped basil, oregano, garlic powder and 1/2 cup Parmesan cheese, until thoroughly blended. Set aside.
Peel onion and slice into rings.
Heat 1 tbs olive oil in a nonstick skillet over medium-high heat. Add onion slices and saute for about 3 minutes, separating rings as you stir. Stir in sugar and continue sauteing until onion begins to brown, about 10 minutes. Remove from pan into small bowl. Set aside.
Remove and discard stems from mushrooms and slice caps into 1/4 inch slices, getting about 8-10 slices from each mushroom.
In same pan used for onions, heat 3 tbs olive oil over medium heat and add mushroom slices. Sprinkle with salt and pepper. Cook about 5 minutes, until mushrooms just begin to give off their liquid. Remove from pan to plate and set aside.
In same pan, cook the sausages until browned on all sides and cooked through. Remove from heat and cool slightly. Cut them crosswise into 1/4 inch slices.
Preheat oven to 375°F Lightly coat a large cookie sheet with nonstick cooking spray ( or use 2 small cookie sheets).
Open biscuits according to instructions on can. Take out 2 biscuits and with one stacked on the other, roll out on lightly floured surface with rolling pin, until 6-8 inches in diameter. Set on cookie sheet. Repeat with remaining biscuits until you have four rounds.
Divide ricotta mixture among the 4 rounds, spreading it out to cover to within 1/2 inch of edge. Use your fingers for this.
Divide mushroom slices among the rounds, then the sausage slices, then the onions.
Sprinkle 2 tbs. Parmesan on each round. Bake for 15-20 minutes, until crusts are done, and toppings are hot. If using 2 cookie sheets, place one on upper rack and 1 on lower rack, and switch them halfway through cooking time. (If making the thinner crust, bake 10-15 minutes).
Remove from oven and cut each round in half and serve.