In a shallow bowl, sprinkle yeast on top of water. Wait for 5 minutes for yeast to turn foamy.
Meanwhile combine sugar, shortening, salt, dry milk, 1 1/2 cups of the wheat flour and the white bread flour in the bowl of an electric mixer. Using a dough hook, mix for half a minute.
Add proofed yeast and knead for 5 minutes, adding more flour as necessary to form a soft and sticky dough.
Place in a lightly greased bowl and cover with plastic wrap sprayed with non stick spray or brushed with a little oil. Cover with a clean kitchen towel. Leave to rise until doubled in size, 45 minutes - 1 hour.
Lightly grease the cavities of a muffin tin with non stick spray or oil.
Transfer dough on a lightly floured board. Divide dough into 12 equal pieces, each one weighing 1.7-1.8 oz. Roll each piece into a smooth ball and place in one of the muffin tin cavities.
Using kitchen scissors, insert open scissors 3/4 of the way into the dough and snip. Repeat this step the other direction, crossing the other intersection. You are essentially cutting each dough ball into quarters. Cover with a kitchen towel and leave to rise until doubled, about 30 minutes.
Preheat oven to 350 F. Brush tops with buttermilk. Sprinkle poppy seeds on top. Bake for 35 minutes.