Heat the oil in a medium stock pot. Add the vegetables to the oil, stir frequently, and cook until lightly brown around the edges.
Add remaining ingredients, except sausage, 1 at a time. Bring to a boil and simmer for 45 minutes to 1 hour.
Stir in sausage and allow to cook for 10 more minutes.
Place in bowls, spoon 1 tablespoon of pesto and 1/4 to 1/2 cup of sausage into each bowl. Serve with Garlic-Parmesan Crostini.
Sauteed Italian Sausage:
Heat the olive oil in a large skillet over high heat. Season the sausage with salt, to taste, and carefully place in a single layer across the skillet. Cook the sausage for 3 to 5 minutes over medium-high heat or until browned. Turn the sausages and repeat on opposite side. Remove from heat and allow to rest for 5 minutes. Slice into 1/4-inch slices.
Combine all ingredients in a food processor and puree until smooth.
Garlic Parmesan Crostini:
Preheat the oven to 400 degrees F.
Heat the oil in a small skillet. Add the garlic and cook for 5 minutes or until garlic begins to brown. Remove from heat. Brush the garlic oil on the top and bottom of each slice of bread. Place the bread in a single layer over a sheet pan. Sprinkle each slice with parmesan. Bake for 10 to 15 minutes on the middle oven rack until bread browns over the top. Serve.