Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan, or line with parchment paper.
Step 2: In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, nutmeg, and salt. Set aside.
Step 3: In a separate medium bowl, whisk together the eggnog, egg, vegetable oil (or melted butter), and vanilla extract until well combined.
Step 4: Pour the wet ingredients into the dry ingredients. Stir with a spatula or wooden spoon just until combined. Be careful not to overmix; a few lumps are okay.
Step 5: To make the crumb topping, in a small bowl, combine the flour, brown sugar, and cinnamon. Add the cold butter pieces. Use your fingertips or a pastry blender to cut the butter into the dry ingredients until coarse crumbs form.
Step 6: Pour the bread batter into the prepared loaf pan and spread evenly. Sprinkle the crumb topping generously over the batter.
Step 7: Bake for 50-60 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean. If the topping starts to brown too quickly, you can loosely tent the loaf with aluminum foil.
Step 8: Once baked, remove the loaf from the oven and let it cool in the pan for 10-15 minutes before carefully transferring it to a wire rack to cool completely. Slice and serve warm or at room temperature.