Warm medium bowl by swirling some hot water in it; Drain. Place yeast in bowl & pour on warm water. Mix in sugar with fork; let stand until yeast has dissolved & starts to foam, 5 - 10 minutes.
Use wooden spoon to mix in salt and about one-third of flour. Mix in another third of the flour, stirring with the spoon until the dough forms a mass and begins to pull away from the sides of the bowl.
Knead 8-10 mins on floured board, working in remaining flour a little at a time. Dough should be elastic and smooth; Form into a ball.
Place dough in lightly oiled mixing bowl, rotating it to grease dough's surface. Cover bowl with moist towel; let stand in warm place until dough has doubled, about 40-50. (To test if risen enough, poke two fingers into dough. If indentations remain, the dough is ready.
Punch dough with your fist to release air. Knead for 1 to 2 minutes, then divide into two balls. Pat into flat circles on a lightly floured surface. Roll to 1/4 inch larger than size of the pan for the rim of the crust.
Place in a lightly oiled pan, folding extra dough under to make a thicker rim around the edge; brush on a light coating of olive oil.
Preheat oven to 350 degrees F. Gently melt butter in a small sauce pan and remove from heat. Stir in Parmesan and cream. Return to heat and bring just to boil at a lowest setting - stirring frequently. Stir in spinach. Add salt and garlic to taste.
Spoon the Alfredo and spinach onto crusts. Top with shredded mozzarella and additional Parmesan. Bake pizzas individually for 20 minutes or until bottom is nicely browned.