Heat a little olive oil over medium heat and once hot fry onion and garlic in it until translucent.
Add tomato paste and carrots and mix well.
Add tomato sauce and water and bring to the boil, once boiling add lamb cubes, thyme, basil, salt and pepper and reduce heat to simmer.
Simmer for a total of 2.5 hours.
After 1 hour 45 minutes wash, peel and quarter potatoes and put in a large pot with water covering the potato quarters completely.
Boil potatoes until tender (approx. 20 minutes once water is boiling). Use a wooden pick to proof if they are tender.
Drain potato quarters in a colander and then transfer back into the pot, add cream, milk, butter and salt and using an electric hand mixer (not a blender, a mixer, or if you don't have one a potato masher) and mix all ingredients together.
Season both potato mash and stew to taste with salt and pepper and serve hot.