Beef And Portobello Minestroganoff

Name: Beef-And-Portobello Minestroganoff
Ingredients: 1 1⁄2 tablespoons extra virgin olive oil; 2 carrots, peeled and chopped; 1 small onion, chopped; 2 portobello mushroom caps, gills removed, halved and thickly sliced; 1⁄2 lb ground beef; salt and pepper; 4 cups chicken broth; 1 (15 ounce) crushed tomatoes; 1 cup tiny pasta, such as ditalini; 1⁄4 cup sour cream