Thoroughly wash spinach under running water to remove all dirt. Remove excess water and finely chop. If the stalks are not too big, add the stalks too. On medium flame, heat butter in a deep pot. Add garlic and saut̩ till they start to brown. Add chopped onions and saut̩ till they turn translucent. About 3-4 mins. Next goes in the chopped spinach. Mix well and cook for another minute. Now add about 2 cups of water, mix well and cook covered for 5-6 minutes till there is a boil. Remove from heat and allow to cool slightly. Blend the soup to a smooth consistency and return to heat. Add yogurt, garam masala and salt and pepper. Cook covered for another couple of minutes. Note: If you want to add cornflour, mix about 2 tbsp cornflour in �_ cup cold milk and add to the soup at this stage. Mix well so that there are no lumps and while cooking, stir continuously till there is a boil. Serve hot garnished with croutons and cheese shavings or a dollop of yogurt.