Preheat broiler.
Cut peppers in half vertically. Remove stem, seeds, membranes. Slit vertically to get them to sit as flat as possible.
Line a baking sheet with foil or parchments.
Place peppers and unpeeled garlic on the baking sheet. Broil on highest rack position about 15 minutes. Pepper skins should be black and bubbly for the most part. Garlic will be roasted and browned.
Remove pan from oven and place peppers inside a covered container. Allow them to sit for about 15 minutes to steam inside container.
Saute onion in oil in bottom of dutch oven until translucent while peppers are steaming.
With a sharp paring knife peel off blackened skin from peppers and discard. Peel garlic cloves.
Blend pepper, garlic and onion in blender until smooth. (This can be done a day ahead if desired and refrigerated.)
Add pepper mixture back into dutch oven. Add broth, salt, pepper, oregano and hot sauce to dutch oven. Bring to a simmer and heat over medium low heat for about 20 minutes.
Remove from heat and add sour cream. Garnish with crushed dried oregano or fresh oregano and serve.