In a large bowl, whisk together the 3 cups of whole wheat bread flour, salt and instant yeast. Stir in warm milk, honey and melted butter. Beat until smooth. Stir in white bread flour (or additional whole wheat bread flour), ½ cup at a time, to form a soft dough.
In a stand mixer fitted with the dough hook or on a floured surface, knead the dough until elastic and smooth, 8-10 minutes.
Use the oil to grease a large mixing bowl. Place the dough in the greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, 1 ½ - 2 hours.
Punch down dough. Turn onto a lightly floured surface and cut the dough into two equal parts. Shape each piece of dough into a loaf. Place in two greased 9 x 5-inch loaf pans. Cover and let rise until doubled, 1 – 1 ½ hours.
Bake at 375 degrees F for 30-35 minutes, or until the loaves are golden brown and they sound hollow when tapped. Remove from the pans and cool on a wire rack for at least 1 hour before slicing.
Tip: for a super-soft crust, brush the tops of the bread with melted butter while the bread is still warm.