Place a rack in the top third of the oven and preheat to 350 degrees F (175 degrees C). Butter and flour a 9x5-inch loaf pan.
Melt butter in a small saucepan over medium heat; simmer, stirring frequently, until butter is browned, fragrant, and foamy, with brown bits in it, 10 to 20 minutes. Stir in hazelnut oil. Set aside until cool but not set.
While butter is cooling, sift whole wheat flour, baking soda, garam masala, cinnamon, and salt into a large bowl.
Whisk 1 cup sugar, eggs, squash, and milk together in a smaller bowl. Whisk in the still-melted butter. Fold in the flour mixture and most of the almonds.
Pour the batter into the prepared pan. Sprinkle remaining almonds and 1 1/2 tablespoons sugar on top.
Bake in the preheated oven until edges have browned and center is set, 50 to 60 minutes. Do not overbake; cake should be moist.
