Preheat oven to 400 degrees F. Place oil into a sauté pan and set over medium high heat. Add onion and sauté 5 minutes. Add the garlic and stir to combine. Grind the lamb in a food processor and add the lamb to the onion mixture. Salt and pepper to taste. Cook 2 minutes thten add the flour and stir. Add the tomato paste or ketchup, beer, Worcestershire, rosemary, lima beans and stir. Bring the mixture to a boil, reduce heat to low, cover and simmer 10 minutes. Spread mixture into a glass baking dish. Mix potatoes, carrots and half and half in a food processor. Top with potatoes, sealing the edges. Bake for 25 minutes or until the potatoes begin to brown. Cool for 20 minutes before serving.