Preheat the oven to 350 degrees. Grease an 8x8-inch baking dish with non-stick cooking spray or melted butter.\nIn the bowl of an electric mixer fitted with the paddle attachment, cream together the butter and sugar until smooth and creamy. Add in the bananas, vanilla extract, baking powder, India spice and salt. Continue beating until combined. \nIn a separate mixing bowl, whisk together the eggs, sour cream and milk. With the mixer on low, add in half of the sour cream mixture, followed by half of the flour. Repeat until all ingredients have been added and the batter is well combined (some lumps are okay). \nMake the streusel topping: In a large mixing bowl, mix together the sugars, cinnamon, salt and India spice. Stir in the melted butter until coated. Using a fork, gently mix in the flour until just combined with some large clumps remaining. \nPour half of the batter into the prepared baking dish and spread in an even layer. Top with a thin layer of streusel topping, followed by the remaining batter. Top with the remaining streusel crumble, pressing the topping lightly into the batter. Transfer to the oven. \nBake until golden brown and a toothpick inserted into the center comes out clean, about 50 - 55 minutes. Slice and serve!