1. Prepare the turkey patties: in a large bowl, mix the minced turkey, onions, Dijon mustard, and breadcrumbs.
2. With this preparation, make patties. Using a fork, flatten the patties.
3. In a pan, heat the olive oil. Add the patties and cook, over medium heat, for 4 minutes on each side.
4. Cut the buns in half to open them. Brush the buns with bell pepper jelly. Add slices of cornichons and tomatoes. Place a turkey patty on each bun.
5. Serve immediately.