Preheat the oven to 350 degrees. Prepare two 4-inch-by-8-1/2-inch loaf pans; grease the bottom and sides of each pan with butter and dust lightly with flour. Set aside.

In a mixing bowl, use the back of a large fork to mash together the bananas, Greek yogurt, milk and ginger. The mixture should be well-mixed with small chunks of banana remaining. Add to a stand-up mixer. With the mixer running on low speed, add the vanilla, butter, egg whites and sugar, until well-combined.

Sift together the flour, baking soda, cinnamon, cloves, nutmeg, salt, and cardamom, if using. Add the dry ingredients to the mixer, a half cup at a time until just mixed. Be careful not to overbeat. Pour the batter into the prepared loaf pans.

Bake for 1 hour, until the tops are golden brown and a cake-tester inserted into the middle of each loaf comes out clean. Remove the pans from the oven and let cool on a baking rack for 10-15 mins. Run a knife around the edge of the pans, and gently flip over to remove the loaves. Let cool completely on a baking rack. Slice and serve.

The bread can be stored for up to a week, if refrigerated and wrapped in aluminum foil or plastic wrap. It will continue to get more moist over time.