In a large soup pot or Dutch oven (or in the insert of a slow cooker), heat the olive oil or butter over medium heat. Add the onion and sauté until softened and lightly golden in spots, about 5 minutes. Add the garlic and sauté for an additional minute or until fragrant.
Stir in the tomatoes along with a few dashes of Worcestershire and hot sauce. (You may add more later, to taste, if desired.) Bring to a boil, and then cover, reduce heat, and simmer gently for 10 minutes. (You may reduce heat to low, partially cover, and let cook a little longer if you like.)
Stir in the cream cheese and sour cream. Helpful hint: Use a whisk to more easily incorporate these cheeses into the hot soup. Then stir in the pepperjack cheese. Heat just until the cheese melts and is fully incorporated into the soup, stirring constantly. Do not bring to a boil at this point. Adjust seasonings to taste and serve hot with croutons, if desired.
Slow cooker method: If your slow cooker doesn’t have an insert that allows for sauteing, transfer the onions and garlic to your cooker after cooking them on the stovetop. Add the remaining ingredients, except the pepperjack cheese and sour cream, and cook on low for 2-3 hours. When ready to serve, whisk in the sour cream and pepperjack, stirring to melt and fully incorporate. Enjoy with or without optional croutons.