In a medium bowl mix together the water, milk, and butter. Microwave for about a minute until the mixture is warm to the touch but not hot. Stir until the butter melts. Add the yeast and honey and stir. Let the mixture rest for 2 minutes.

Add the salt, egg, and whole wheat flour and mix well for 3 minutes. Add the old fashioned oats and ½ cup of the all-purpose flour and stir for another 3 minutes. Add additional flour, about ¼ cup at a time, and stir well after each addition.

When the dough starts to come together, remove it from the bowl and place it on a well floured surface. Knead in additional flour until a smooth dough forms. Add a little cooking spray to the bowl you used, form the dough into a ball, and place it back in the bowl. Cover the bowl with plastic wrap and let it rest for 30 to 45 minutes.

When the dough has risen for 30 to 45 minutes, remove it from the bowl and divide it into 12 even parts. Shape each dough piece into a wide flat circle that is about 4 inches across. Lay the shaped buns on a parchment or baking mat lined baking sheet, about 2 inches apart. Repeat with remaining dough. I could fit 6 buns per baking sheet. Cover the dough with a towel and let it rise until it is light and puffy, about 40 minutes.

Preheat the oven to 375°F. Add the egg yolk and water to a small bowl and mix it together well with a fork. Use a pastry brush to brush the egg wash over the buns and then sprinkle the bun tops with a few additional oats (you could also use a few sesame seeds).

Bake the buns for 12-15 minutes until the tops are golden brown. Remove from the oven and let cool. Slice in half before serving.