Combine the yeast, sugar, warm water, yogurt and 2 tablespoons of melted butter in a large bowl. Whisk the flour and salt together in a separate bowl. Stir the flour into the wet ingredients, adding more flour as needed for the dough to come together as you stir with a wooden or in a stand mixer with dough hook. The dough should be sticky, but you’ll need to add enough flour to make it manageable. Knead the dough on a floured surface by hand or with a stand mixer for about 5 minutes, until it is a less sticky and more smooth.