Add butter and olive oil to the soup pot. Then add the chopped onion. Stir the onion around to get it fully coated with the olive oil and butter. Add the salt and pepper and continue to saute until the onion is translucent. Add the garlic for just a few moments before turning off your heat. You want the onion fully cooked, and the garlic just warm enough to help release the flavor. If you cook the garlic too long, it could burn and turn bitter.