Chop the bacon into small dice.5 slices bacon

Place a large skillet or frying pan over medium heat, add the bacon and cook for 8-10 minutes until crispy. Use a slotted spoon to remove the bacon from the pan, leaving behind the bacon fat/grease.

Use kitchen paper to pat each chicken breast. A dry chicken breast won't slip and slide on your cutting board.2 chicken breasts

Place the chicken smooth side up on your board and use a sharp knife to cut sideways through the breast, as though you are opening it up like a book (see picture below)

Try to keep the knife flat and parallel to the chopping board.

Continue cutting through the breast until you have two fillets.

If you find they are not thick, cover the fillet with parchment paper and use the smooth side of a meat mallet (or a heavy-based pan) to gently flatten the plumper end.

Add the flour to a shallow dish.¼ cup all-purpose flour

Season the chicken fillets on both sides with salt and pepper, then coat them lightly in the flour. (don't discard the flour yet)½ tsp kosher salt½ tsp black pepper

Add the butter to the bacon fat, and once melted, add the floured chicken fillets to the pan.1 tbsp butter

Cook chicken for 3 minutes per side, until golden brown. Remove the fillets to a plate, tent with foil, and set aside.

Turn the heat up to high and add the mushrooms to the pan; cook for 3-4 minutes until they are browned.2 cups sliced mushrooms

Remove the mushrooms from the pan. (I put them on the same plate as the chicken)

Turn the heat on the pan to low, add the butter and the chopped onion, stir well and cook for 2-3 minutes until softened.1 tbsp butter1 small onion

Add the minced garlic and two tablespoons of the remaining dredging flour to the onions and stir to coat. (see note 8)2 garlic cloves

Slowly whisk in the chicken broth and sherry (if using).¾ cups chicken broth/stock2 tbsp dry sherry

Bring to a simmer and cook gently for a minute.

Add the heavy cream, mustard, salt, and pepper to the pan and stir well.1 ¼ cups heavy cream½ tsp Dijon mustard¼ tsp salt¼ tsp black pepper

Add the chicken and mushrooms back into the pan, plus any collected juices. Simmer together for another 3 minutes until the sauce has thickened, and the chicken is heated through.

Sprinkle over the cooked bacon, season to taste, and serve. Garnish with parsley (optional)