Preheat oven to 400°.
On a baking sheet coat garlic, onion, tomatoes, in olive oil, season with salt and pepper. Place garlic and tomatoes cut side down and roast until vegetables are softened and blistered in spots, 10–15 minutes. Set aside.
Heat a dry skillet. Add dried chilies and just warm the chilis to draw out more flavour, being careful not to burn or toast them. Remove the chilies and set them aside.
In a saucepan add all the sauce ingredients: Chilies, garlic, onion, tomatoes, stock. Bring to a boil and then simmer for 10 minutes.
Pour the sauce through a fine mesh strainer and reserve the liquid.
Place strained peppers, onion, garlic, tomatoes in a food processer. Add some of the reserved liquid. Puree into a smooth paste.
In a skillet heat 2 tablespoons of olive oil. Add the chili paste. Stir and heat for one minute. Add the reserved liquid until it forms a thin sauce. Simmer for 10 minutes. Season with salt and pepper to taste.