Step 1: Preheat your oven to 350°F (175°C). This ensures that your muffins bake evenly and rise beautifully.
Step 2: Grease your muffin tin with a little butter or line it with paper liners to prevent sticking.
Step 3: In a large mixing bowl, whisk together the unbleached all-purpose flour, baking soda, salt, and ground nutmeg. Set aside.
Step 4: In another bowl, mash the ripe bananas until smooth. Then, add in the granulated sugar, dark brown sugar, melted butter, milk, and egg. Whisk until well combined and smooth.
Step 5: Pour the wet ingredients into the bowl with the dry ingredients. Use a spatula to fold the mixture gently until just combined. Be careful not to overmix; a few lumps are okay!
Step 6: Fold in the toasted and finely chopped macadamia nuts until evenly distributed throughout the batter.
Step 7: Scoop the batter into your prepared muffin tin, filling each cup about 2/3 full to allow for rising.
Step 8: Place the muffin tin in the preheated oven and bake for 18-22 minutes, or until a toothpick inserted into the center comes out clean.
Step 9: Once baked, remove the muffins from the oven and let them cool in the pan for about 5 minutes. Then, transfer the muffins to a cooling rack to cool completely.