Cut the chicken breast into 4 pieces and pound flat. Season with salt and pepper.
Trim the crust off the baguette slices and score the bread into squares on one side.
Assemble the "sandwich": bread + chicken + bread. Fry in a pan brushed with vegetable oil on both sides - this happens very quickly.
Transfer the chicken in bread to a baking sheet and bake in a preheated 180 °C (355 °F) oven for 20 minutes.
Brush the finished chicken with mustard, press garlic over the top and sprinkle with fresh herbs. Enjoy!