Mushrooms, Spicy Italian (Funghi Piccanti) II

Ingredients

• 1 to 2kg (2.2 to 4.4 lb.) small mushrooms, thinly sliced
• 1 medium onion, thinly sliced
• 3 large cloves of garlic, minced
• 4 tbsp. extra-virgin olive oil
• 1 to 2 firm ripe tomatoes, coarsely chopped
• 1 tbsp. kosher salt
• 1/2 tsp. ground chili pepper, or to taste
• 50ml (3 tbsp. + 1 tsp.) white wine vinegar
• 1 tbsp. capers (optional)
• 1 tbsp. minced Italian parsley