Chorizo And Chestnut Soup

Name: Chorizo And Chestnut Soup
Ingredients: 2 tsp Olive Oil; 1 large onion, peeled and diced; 1 medium carrot, peeled and diced; 1 x celery stick, chopped; 8 oz Spanish cooking chorizo cut into 1/2-inch cubes; 1 1/2 cloves Garlic Clove; 1 tsp Ground Cumin; 1 1/2 tsp finely chopped fresh thyme leaves (or 1/2 teaspoon dried); 1/2 tsp chili flakes or cayenne pepper (or to taste); 3 can canned plum tomatoes, drained and roughly chopped; 1 lb shelled chestnuts, fresh or vacuum-packed, roughly chopped; pinch (about 20) saffron threads, crumbled; 4 cup Water; 1 lb fresh chard or kale, tough stalks removed, washed and cut into ribbons (optional); 1/2 tsp salt and pepper