To prepare the sweet potato mash place the peeled and cubed sweet potatoes in a pot of salted water and bring to the boil or alternatively steam. When soft drain then mash with a little butter until smooth.
In a pan, brown the onion in oil. Add the carrots, tomatoes and mushrooms and cook until soft.
Add the lentils and water to the pan, stir in the contents of the pouch and the tomato paste and bring to the boil while stirring.
Reduce heat and simmer uncovered for 10 minutes, stirring occasionally. Serve with sweet potato mash.