Dissolve yeast and sugar in 1/3 of the warm water. Let stand 5 to 6 minutes, until mixture is foamy.
In a large bowl, mix together 1/2 of the remaining flour, remaining water, salt, oregano and butter. Add yeast mixture, and stir to combine. Work in remaining flour a little bit at a time until a soft dough forms.
Transfer dough to a lightly floured surface, and knead for 10 minutes. Put dough in a well oiled bowl covered with a damp cloth, and let rise until tripled in bulk.
For a round pizza, break off about 1/4 of the dough. Grease a large round baking tray, and sprinkle lightly with polenta. Roll out the dough to fit the pan, stretching it to fit. Brush pizza base with olive oil, and sprinkle with cheese. Add desired toppings.