Whole wheat hamburger buns

This variant on my basic bread recipe may be a way to make yourself feel altogether healthier about eating hamburgers. I don't like those white plastic buns everyone eats with hamburgers, and these seem much more substantial. I haven't figured out a way to make completely whole-wheat buns that are soft enough, but a 50-50 compromise is better than nothing, no?

Makes 8 buns.

Ingredients
1 cup warm water
2 teaspoons active dried yeast
2 teaspoons sugar or honey
1 teaspoon salt
2 tablespoons extra virgin olive oil (or any other kind of oil; olive tastes best)
1 1/2 cups white flour (bread flour has a higher gluten content, but plain will work too)
1 1/2 cups whole wheat flour
Kosher salt, sea salt, or reasonably finely ground rock salt
1 tablespoon butter

Whisk the first three ingredients together in a large bowl. Leave for ten minutes in a warm-ish place, or at least a place where there aren't any cold drafts, until the yeast starts going into fluffy bubbles.

Sprinkle the salt over the mixture and add the olive oil. Give it a stir.

Whisk the two flours together in a medium bowl.

Add 2 1/2 cups of the flour mixture and stir with a wooden spoon to form a ball of sticky dough.

Turn the dough out onto a generously floured counter top and knead the dough for around 5 minutes, adding the extra half-cup of flour little by little to stop it sticking to the counter. You know you've kneaded it enough when the dough is smooth and satiny-textured and doesn't stick to the counter or your hands.

Wash and dry your bowl, then coat the inside with a little oil. Place your dough in the bowl, cover the bowl with a clean towel, and leave it in a warm place until the dough has roughly doubled in size. Depending on how warm the warm place is, this can take as little as 30 and as many as 120 minutes. If your oven has a bread proof setting, you can put it in there. Make sure, obviously, that you use a metal or glass bowl if you do this.

When the dough is risen, knead it again briefly to get some of the air out. (It will make a satisfying whoosh.) Divide the dough into 8 equal pieces and shape the into buns. Place them on a baking sheet lined with baking paper.

Heat your oven to 430 Fahrenheit (220 celsius). Right before baking, throw a couple of handfuls of ice cubes into the bottom of the oven to help keep the buns moist. Bake the buns for 12-15 minutes or until they're golden on top and slightly golden underneath.

Take the buns out of the oven and transfer them to a wire rack. Melt the butter and brush the tops of the buns with it, then leave them to cool. (The butter helps them to stay soft enough for hamburgers.)