Preheat the oven to 350ºF. Line a loaf pan with parchment paper.
In a tiny bowl, combine all spices to make your chai spice mix. Set aside.
In a large bowl, combine the mashed bananas with the melted butter, stirring to combine. Mix in both sugars, the eggs, greek yogurt, and vanilla.
Fold in flour, baking soda, salt, and a little over half the chai spice mix, mixing until well combined. Pour batter into prepared loaf pan.
In a separate bowl, mix together the cashews, sugar, flour, melted butter, and the remaining chai spice. Use your hands to work the streusel together, then sprinkle the streusel evenly over the loaf, covering it entirely with streusel.
Bake the loaf for 45 minutes or until a knife comes out clean when inserted into the center of the loaf. If your streusel begins to get golden before the first 30 minutes of cooking, gently cover the top of the loaf with tin foil. This will prevent excess browning.