Heat 2 tablespoons of the olive oil in a large pan over medium-high heat. Cook chorizo, stirring, for 2 minutes or until browned. Add garlic, onion, mushrooms, oregano, basil and half each of the olives and chillies. Cook, stirring, for 4 minutes or until onion has softened. Stir in tomatoes, bring to a simmer, then cook, stirring occasionally, for 10 minutes or until sauce is slightly thickened. Season with salt and pepper.