
Start by placing the whole chicken breast in a pan with the mustard.
Take to a preheated oven at 180° C (350° F) and bake for 30 minutes.
In a large pot, place the medium potatoes cut into small cubes and enough water to cover everything.
Turn on the heat to medium and cook for 15 minutes.
Transfer to a large bowl, add the unsalted butter, the salt and mash everything very well until it becomes a smooth purée.
Add the grated Parmesan cheese, mix once more to incorporate and set aside.
After the chicken has finished cooking in the oven, remove it from the pan.
Season with the salt, the black pepper and the chimichurri.
Flip it over and repeat the same seasoning on the other side.
In a large skillet over medium to low heat, add the unsalted butter, the peeled garlic clove, the sprig of rosemary and stir everything very well until the butter is completely melted.
Add the chicken we seasoned earlier and fry until both sides are golden brown.
Finally, cut the chicken into strips.
Serve.