Ingredients:
2 - 3 skinless chicken breast fillets, cut into large-sized chunks
2 carrots - chopped
2 stalks celery - stringy bits removed and sliced
1 clove garlic - finely chopped
1 large onion - peeled and sliced
1 leek - cleaned and sliced
4 mushrooms - sliced
1 heaped Tbsp mustard
1 tsp dried mixed herbs
1 bay leaf
Pinch of black pepper and salt (to taste) the stock and gravy will be fine
1 pkt or 2 cubes of chicken stock mix
300 ml boiling water 
Chicken Gravy Mix to thicken at the end of cooking

Method:
Add all the ingredients to the slow cooker. Dissolve the stock pot sachet or stock cubes in 300 ml of boiling water and add. Give everything a good stir to mix together.
Place the lid on the slow cooker and set it on Low for 7 to 8 hours, or High for 4 to 6 hours, but please check your slow cooker instructions.
When it's cooked nicely, remove the bay leaf and discard.
Turn the slow cooker to High and stir in the chicken gravy mix, a little at the time, so you don't end up with gravy lumps. Add enough to thicken to your liking.
Leave the lid off and let it thicken for a few minutes. Taste and check the seasoning is right.

Serve with mashed potatoes and toasty bread.