Combine yeast and water in a medium-sized bowl and let dissolve for 10 minutes. Add remaining ingredients and mix until incorporated and smooth. Cover bowl with a clean towel and let sit for about 30 minutes, until the dough has doubled in size. Preheat oven to 350 degrees.

Once the dough has risen, turn onto a well-floured surface, and roll into a rectangular shape with a rolling pin or a sturdy glass. Place dough on a baking sheet or stone and bake for 20 minutes, or until the crust is golden brown. Once baked, cut out circular shaped pieces of bread to fit on top of the ramekin.

Slice onions into thin crescent-shaped slices. In a large pan, melt butter over low heat, then add onions and salt, and let caramelize on low, for about 30 minutes. Add wine and broth and cook over medium heat until reduced by a third.

Pour soup into the ramekins, until 2/3rds full. Top with bread, then cheese and bake in a preheated oven at 350 for 5-10 minutes, or until cheese has melted.