Melt the butter over medium heat in a large saucepan. Cook and stir the onion and garlic in the melted butter for about 5 minutes, until onion is translucent. Sprinkle in curry powder, garam masala, paprika, sugar, ginger, turmeric, salt and pepper. Continue to cook and stir 3 to 4 more minutes until spices are lightly toasted.
Mix in the chickpeas, potatoes, coconut milk, tomato, milk, tomato puree, sour cream and stock cubes. Simmer the curry over medium-low heat for about 25 minutes until the potatoes are tender. Stir in ground almonds to thicken.
Garam masala is a basic blend of ground spices common in Indian cooking. Make your own with this recipe.