Meanwhile, heat the olive oil in a large sauce pan over medium-high heat. Add onion and carrots, and sauté for about 5-7 minutes. Add garlic, peas and corn, sauté for 2-3 minutes. Stir in the flour and cook for 1 more minute. Whisk in the chicken stock until it is combined, then stir in the milk, heavy cream, salt, pepper and tuna. Continue cooking, stirring occasionally, for an additional 5 minutes.