Warm oil over medium high heat in a pot. Add in salt, thyme, garlic, and basil. Let it cook for a minute before adding the remaining soup ingredients.
Lower heat to medium once soup begins to simmer. Let it cook for half an hour before removing the thyme and garlic.
Lower heat to low and once soup begins to cool, gently blend with a hand immersion blender until the soup is creamy and has thickened.
To make the roux, melt butter over medium high heat in a small pan. Once butter melts, add flour and cook for 2 minutes -stirring occasionally. Once flour cooks, slowly whisk in milk, and keep adding heavy cream until the roux is creamy and soft, like Greek yogurt.
Gently pour in the roux mix to the tomato bisque, and whisk until tomato bisque thickens.
Taste for seasoning and adjust with salt, if desired.