Preheat oven to 400 degrees F.
Bring milk, water, ¼ cup olive oil and 1 teaspoon salt to a boil.
Stir polenta in slowly to avoid lumps. Turn heat down to low. Stir until polenta is thick (about 5 minutes for instant polenta). Remove from heat.
Oil a cookie sheet or pizza pan. Add polenta and press down to desired pizza thickness (I like a fairly thin crust).
Bake in oven for about 35 minutes.
While crust is baking, saute onions and mushrooms in ¼ cup olive oil for about 3 minutes. Add wine, ¼ teaspoon salt and thyme. Saute until liquid has dissipated (about 3-5 more minutes). Remove from heat.
Remove crust from oven. Top with tomato sauce, onion/mushroom mixture, cheese and olives.
Bake for another 15 minutes.