Vegan Roasted Corn Chowder

Name: Vegan Roasted Corn Chowder
Ingredients: 9 ears fresh corn on the cob, silks and husks removed; 1 small Spanish or yellow onion, coarsely chopped; 1 medium carrot, coarsely chopped; 2 tablespoons olive oil; 1 tablespoon unsalted butter or vegan buttery spread; 3 large cloves garlic; 2 cups low-sodium chicken, vegetarian stock or water (optional); 2 teaspoons agave nectar (optional)