Mix yeast solution into egg yolk with a fork. Beat in flour. Turn out dough onto floured board and knead until smooth. Place kneaded dough in a flour-sprinkled bowl and cover with a damp cloth. Let rise in a warm place for two hours, or until doubled in bulk.
The dough can now be split into two pieces. You can try to roll it into a circle if you have a pizza pan, or just do your best and use cookie sheets.
Spread sauce lightly and evenly over prepared crusts. Sprinkle each with 1/2 pound of the cheese. Top with toppings. Bake at 450º F for 15 minutes.
Brush your crusts with a little olive oil, then sprinkle them lightly with garlic powder. Spread a thin layer of ricotta over each crust, then top each pizza with 1/2 pound mozzarella. Bake at 450º F for 15 minutes