2 packages active dry yeast
1/2 cup warm water (105 to 115 degrees)
2 cups warm milk (105 to 115 degrees)
2 tablespoons vegetable oil, plus more for bowl and baking pans
1/2 cup firmly packed brown sugar
2 teaspoons salt
2 cups old-fashioned rolled oats (not instant), plus more for topping
1 teaspoon ground cinnamon
4 1/2 to 5 1/2 cups unbleached all-purpose flour
2 cups chopped apples (such as Granny Smith)
1 cup coarsely chopped walnuts, lightly toasted
In a large bowl, soften the yeast in the water. Add the milk, oil, brown sugar, salt, oats, cinnamon, 2 cups of flour, apples, and walnuts. Beat vigorously with a dough whisk or heavy-handled spoon for 2 minutes. Gradually add more of the remaining flour, 1/4 cup at a time, until the dough forms a mass and begins to pull away from the bowl. Turn the dough out onto a floured work surface. Knead the dough, adding more flour a little at a time as needed, for 8 to 10 minutes, until the dough becomes elastic and less sticky.
Form the dough into a ball and turn it in a large oiled bowl to coat it all over with oil. Cover with a towel or plastic wrap and let it rise in a warm, draft-free place, until it is doubled in size, about an hour.
Oil two standard loaf pans. Punch the dough down, divide it in half, and one at a time form into a loaf. Flatten the dough into a rectangle the length of a pan and roll it into a cylinder, pinching the seam closed. Fold the dough on the ends as if wrapping a package and pinch closed. Fit the dough into the pan, seam side down, and repeat with the other loaf. Cover the pans with a towel and let rise until nearly doubled, about 45 minutes. About 15 minutes before the end of rising, preheat the oven to 375 degrees.
Just before baking, beat the egg with 1 tablespoon water to make an egg wash and brush the tops of the loaves (don't let it drip). Sprinkle some oatmeal flakes on top. Bake in the preheated oven until the loaves are golden brown (internal temperature should reach 190 degrees), then remove the loaves from the pans. Rap the sides of the loaves with your knuckles for a solid sound; if they don't seem quite done, put them back in the oven on the bare rack for a few minutes longer. Cool the finished loaves on a rack.
Makes 2 loaves.
By Elizabeth Riely, Globe Correspondent