Pre-heat your oven to 180 degrees / gas mark 4.
Chop the chicken breasts into chunks. Heat the olive oil in a frying pan and fry the chicken on a medium heat for 5 minutes until lightly browned. Remove from the pan and set aside.
Whilst the chicken is browning, peel and chop the potatoes into chunks. Boil the potatoes in a saucepan of boiling water for 15-20 minutes until soft. Once cooked, drain and mash them. You can add a splash of dairy free milk to make them a little creamier.
Next, chop and prepare your onion, garlic, carrots and mushrooms.
Chop the bacon into small squares and add to the same pan the chicken was in. Fry for 3-4 minutes until nice and crispy. Once crisp, turn down the heat and and add the garlic, onion, carrots and mushrooms. Fry all together for 2-3 minutes until soft.
In a separate pan, melt the butter. Once melted, add the flour and whisk together. Slowly add the stock, whisking all the time until the sauce has thickened. Add the mustard and dried thyme, then stir well.
Put the chicken back into the frying pan with the bacon mixture, add the sauce and mix together.
Transfer mixture into a casserole dish then top with the mash. Score the mash in a circle pattern with a fork.
Bake in the oven for 45 minutes until crispy.