In a large bowl, mix the flour, brown sugar, shortening, butter and salt with a fork (or clean hands) until it resembles coarse crumbs.
Reserve ¾ cup of the crumble mixture and set aside. Then stir the nutmeg, cinnamon, baking soda and baking powder into the remaining flour mixture.
In a small bowl, whisk together the eggs and buttermilk. Add to the dry ingredients and mix until a smooth batter forms.
Transfer the batter to a greased 9×9-inch baking pan. Spread into an even layer, then top with the reserved crumble mixture.
Bake in a preheated 375°F oven until golden, 30 to 40 minutes. A toothpick should come out clean when inserted in the center of the bread.
Let cool completely, then remove and slice into squares.
