Cut the peppers in half and remove all seeds and membranes. Press the red peppers flat with your hand and lay them on a foil lined, rimmed baking sheet. Place the garlic cloves on the baking sheet.
Set the oven on broil and raise the rack to the upper position. Broil the red peppers and garlic for 15 minutes.
Once the pepper skin has blackened, remove from the oven and place in a large zip bag to steam, about 10 minutes.
Preheat a large heavy pot to medium heat. Add the oil, thyme, bay leaves, and onions. Cook for 10 minutes, until onions are soft.
Add the broth, hot sauce, salt and pepper. Squeeze the garlic cloves out of the peels into the pot.
Then peel the charred skin off each pepper half and place it in the pot.
Reduce the heat, cover, and cook another 20 minutes. Remove the bay leaves and thyme sprigs. Then, using a hand-held immersion blender or standard blender, blend until smooth. *If using a blender, be sure to remove the plug on the lid and cover with a kitchen towel—this with allow the heat to vent without a big mess!
Add the vinegar and salt again if needed.
Serve with extra thyme leaves. In the photos I thinned out a little plain Greek yogurt with milk to make a fancy swirl on top. Pretty, but not necessary.