1. Soften yeast in one-third cup lukewarm water. Add one teaspoon sugar and one cup flour. Mix and then knead until smooth. Place ball of dough in a bowl and cover with lukewarm water. Let rise until ball floats in water, about one hour or less.
2. Put remaining flour in a large bowl. Add the ball of dough, half the butter, remaining sugar, salt and two of the eggs, slightly beaten. Mix well with the fingers, adding enough milk to give a soft, nonsticky dough. Turn out on a lightly floured board and knead until smooth.
3. Work in the remaining butter and two more eggs. Repeat the kneading. Lift the dough and slap or bang it on the table until it is very smooth.
4. Add two more eggs, work them into the dough and repeat the kneading and banging on the table.
5. Shape the dough into a ball and place it in a greased bowl. Cover and let rise in a warm place (80° to 85° F.) until double in bulk.
6. Punch and stir the dough down. Shape into a ball, place in a clean greased bowl, cover tightly with foil and chill overnight or slightly longer.
7. To shape the brioche, turn the dough out onto a floured board. Cut off about one-sixth and reserve for topknots of buns. Divide remainder of the dough into eighteen to twenty-four portions and shape each into a ball. Place in greased brioche pans or muffin tins (2 3/4 x 1 1/4 inches deep). Cut reserved dough into the same number of small balls. Dampen a finger slightly and make a depression in the center of each large ball. Place a small ball in each of the depressions. Cover and let rise in a warm place until double in bulk, or about one hour.
8. Preheat oven to 450° F. and place rack near bottom.
9. Lightly beat remaining egg and brush over the tops of the brioche. Place in oven and bake until well browned, about fifteen minutes.