Makes 2 medium loaves
Sprinkle dry yeast and sugar over warm milk (105 - 115 F) in large bowl; stir to dissolve. If using cake yeast, crumble yeast into large bowl. Stir in sugar and lukewarm milk (95 F). Let stand until foamy.
Add salt and 2 cups flour. Whisk in until smooth. Using spoon, mix in enough remaining flour to form soft dough. Knead on floured surface until smooth and elastic, kneading in more flour if sticky, about 10 minutes.
Grease large bowl. Add dough, turning to coat entire surface. Cover bowl with plastic. Let rise in warm draft-free area until tripled, about 2 hours.
Gently knead dough in bowl until deflated. Cover and let rise again until doubled in volume, about 1 hour.
Cover 2 baking sheets with oats. Gently turn dough out on lightly floured surface and divide in half. Cut off 2/3 of 1 piece of dough and gently knead into round. Place on prepared sheet; form well in center. Gently knead remaining 1/3 of dough piece into round and set in well atop first piece. With floured finger, make hole down center of both rounds to baking sheet. Repeat with remaining dough half. Cover with waxed paper or towel. Let rise in warm draft-free area until doubled in volume, abut 30 minutes.
Preheat oven to 425 F. Brush loaves with glaze. Bake until golden brown and loaves sound hollow when tapped on bottom, about 35 minutes. Immediately transfer to rack and cool.