Melt the butter with the oil over low heat in a heavy bottom pot.
Add the onion; wilt over low heat for 8 to 10 minutes. Add the garlic during the last 2 minutes, stirring.
Add the tomatoes and broth. Bring to a boil, reduce heat to a simmer and cover; cook over medium-low heat for 60 minutes. Season with oregano, salt, and pepper.
Add basil. Stir in the cream or half & half, simmer for another 30 minutes.
Garnish with fresh basil before serving.
Note: When tomatoes are in-season use fresh tomatoes, blanch for 8 minutes and process with food processor. In the winter, use a San Marzano-type canned tomato, drain half of the liquid and process in food processor.