Mix together both flours, 3 tablespoons of the sugar, the malted milk powder, salt, and caraway seeds in a medium-size bowl. Set aside.
Make the yeast sponge: Stir the water, yeast, and the remaining tablespoon of sugar in a small bowl until dissolved. Let the mixture stand until it is foamy and light, about 5 minutes.
Meanwhile, using an electric mixer equipped with a dough hook or a paddle, beat the egg and 1/3 cup oil in a large bowl on high until light yellow. Reduce the speed to low and beat in the yeast mixture, then the flour mixture, then 1 cup of the onions.
Knead the flour mixture by beating the dough on high for 15 minutes (the dough will be smooth and elastic).
Transfer the dough to a well-buttered bowl and turn over the dough once to coat it well with the butter (the dough will be sticky). Cover the dough and let it stand at room temperature until it's double its size (this will probably take about 1 hour).
Preheat the oven to 400° F and butter 2 baking sheets. Punch the dough down with your fist to deflate it. Turn out the dough onto a lightly floured surface. Flour your hands and lightly knead the dough until it's no longer sticky, about 2 minutes.
To make dinner-size 4-inch rolls: Cut the dough into 4 equal pieces, then each piece into 3 more equal pieces, using kitchen shears. You will have 12 little mounds of dough. (For small twin rolls, divide the dough into 24 equal pieces.) Flour your hands well. Pick up each piece of dough in the palm of your hand and shape it into a rounded roll with a smooth top. Place the rolls about 2 inches apart on the baking sheets.
Whisk the egg with the 1/2 teaspoon oil and brush this glaze on top of each roll. Sprinkle with the remaining 1/2 cup onions. Cover the rolls and let them rise until light and doubled in size, about 30 minutes more.
Bake the rolls until they are golden and set, about 10 to 12 minutes for the twin rolls, 13 to 15 minutes for the buns.
Serve them warm or at room temperature or use for overstuffed sandwiches. These are outstanding when filled with layers of freshly sliced warm corned beef on the bottom and sliced pastrami on top.Makes 4 to 6 Source: