In a 5-quart saucepan, saute onion, carrots, celery, basil, and parsley in 2 Tbsp butter (or olive oil) until they begin to soften (10-15 minutes).
Meanwhile, melt remaining butter (3 Tbsp) in the skillet, and add flour. Cook on medium heat, stirring constantly, until mixture begins to bubble (3-5 minutes). Add to soup.
Recipe adapted from Taste of Home