Melt butter in a medium saucepan over medium-low heat. Add onion and garlic, and cook stirring until translucent, about 6 minutes.

 

Add tomatoes, stock and oregano. Bring to a boil. Reduce heat and simmer gently until thickened, about 45 minutes. Remove oregano sprigs.

 

Slowly add half and half, stirring constantly. Seaton with salt and pepper. Garnish with a sprig of fresh oregano.