Saute onion in butter over medium heat until lightly browned. Remove from heat and set aside.
Lightly grease three large baking sheets and sprinkle them with cornmeal. Sprinkle yeast over warm water in a mixing bowl. Let stand until yeast is dissolved, then stir in sugar, salt, chopped jalapenos, sauteed onion, buttermilk and 2 cups of the flour. Beat mixture well. Stir in enough of the remaining flour to make dough easy to handle.
Turn dough out onto a lightly floured surface; knead about 5 minutes. Place in a large greased bowl, cover, and let rise in a warm place until double, about 1-1/2 to 2 hours.
Punch down dough and divide into 4 equal parts. On a floured surface, roll out one part dough to form an 8" x 8" square. Using a knife or pizza cutter, cut the square into 8 equal strips. Place the strips onto prepared baking sheet. Repeat with remaining portions of dough. Let rise uncovered (1 hour or more for light, airy breadsticks; 30 minutes for a denser, chewier texture).
Bake in a preheated 400F oven for 10 to 12 minutes, or until golden brown.