
Heat vegetable oil in a thick-bottomed saucepan. Add onion and garlic. Fry for 4 minutes until golden brown. Pour in tomato paste and stir. Simmer for 1 minute. Then add carrots and shells. Salt and pepper. Stir again. Leave for 3 minutes. Pour in water, bring to a boil over high heat. Then reduce heat to low and cook the sauce for 40 minutes. Pour the contents of the saucepan into a blender bowl. Grind into a puree. Rub the sauce through a sieve to remove shell particles.