In large bowl, dissolve yeast in warm water; blend in yogurt and salt. Lightly spoon flour into measuring cup; level off. Add 2 1/2 cups flour. Blend at low speed until moistened; beat 3 minutes at medium speed. By hand, stir in 2 to 2 1/2 cups flour to form a stiff dough.

On floured surface, knead in up to 1 cup flour until dough is smooth and elastic, about 5 to 8 minutes. Place dough in greased bowl; cover loosely with plastic wrap and cloth towel. Let rise in warm place until light and doubled in size, about 1 hour. Punch down dough.

Divide dough into 2 parts; shape into balls. Place on cookie sheet. Cover and let rise in warm place until light and doubled, about 1 hour.

Heat oven to 400 F. With sharp knife, cut 3 slashes across top of each loaf. Brush loaves with water. (This is what is going to give the crisp crust.) Bake for 35-45 minutes, brushing with water every 15 minutes, until loaves sound hollow when lightly tapped. Remove from pan immediately.