Prepare the mussels using a table knife, scraping off any barnacles and remove the beards off the shells - to do this simply pull down sharply to release them. Next it is important to check the mussels are all alive. If any are open give them a tap on a flat surface and if they close they are good to cook and eat.
Heat a large saucepan on the hob or the barbecue bars to a high heat. Add the oil and sauté the shallot, bacon lardons and garlic for 20 seconds with no colour, until softened. Add the grain mustard and stir into the vegetables then pop in all the mussels, cider, pinch of salt and cover with a lid.
Keep the heat high and using a cloth shake the pan and cook for 4 minutes until the mussels are open.
Pour in the cream and stir, add the parsley and serve in bowls with fresh crusty bread.
Note: If any mussels remain unopened discard them when serving up!