1. In a saucepan, boil water and add in the potatoes. Cook until done.
2. In a shallow pan, heat olive oil and add in the onion and sauté for a few minutes.
3. Stir in the garlic, followed by the sausages. Cook for 10 minutes.
4. Pour in the canned tomatoes, cannellini and kidney beans. Simmer for a few minutes on low heat.
5. Strain the potatoes and place in a large bowl.
6. Add in the butter and milk and mash with a potato masher.
7. Serve mashed potatoes along with sausages and beans.