Preheat oven to 425°F.
Combine 2 cups flour, undissolved yeast, sugar and salt in a large bowl. Add warm water heated to 120°F and oil to the bowl; stir until well blended, about 1 minute.
Gradually add enough remaining flour to make a soft dough. Dough should form a ball and will be slightly sticky. Knead on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes. Let dough rest at this point for 10 minutes. Divide dough in half.
Roll dough on a floured counter to 12-inch circle; place in greased pizza pan or baking sheet. Form a rim by pinching the edge of the dough.
Top the dough with pizza sauce. Using a spoon, spread sauce evenly across surface of dough. Top with desired toppings (such as the mushroom and sauteed spinach pizza recipe) and finish with mozzarella cheese. Repeat with second pizza.
Bake for 12-15 minutes, until cheese is bubbly and crust is browned. For best results, rotate pizzas between top and bottom oven racks halfway through baking.