Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it with cooking spray.
In a small bowl, combine 1/2 cup of all-purpose flour, 1/4 cup of granulated sugar, 1/2 teaspoon of ground cinnamon, and 1/8 teaspoon of salt. Pour in 1/4 cup of melted unsalted butter and mix until crumbly. Set aside.
In a large mixing bowl, whisk together 3 cups of all-purpose flour, 3 teaspoons of baking powder, 1/4 teaspoon of ground nutmeg, and 1/2 teaspoon of salt.
In another bowl, beat together 1/2 cup of unsalted butter at room temperature, 1 cup of granulated sugar, and 1/4 cup of packed light brown sugar until light and fluffy. Add 1 teaspoon of finely grated orange zest and mix well.
Beat in 2 large eggs and 1 egg yolk until combined. Stir in 1 and 1/2 teaspoons of vanilla extract and 1 cup of whole milk until fully incorporated.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix.
Gently fold in 8 ounces of roughly chopped dark chocolate and 1 and 1/2 cups of fresh or frozen raspberries.
Spoon the batter into the prepared muffin tin, filling each cup about 3/4 full. Sprinkle the crumb topping generously over each muffin.
Bake in the preheated oven for 20-25 minutes or until a toothpick inserted into the center comes out clean. The tops should be golden brown.
Allow the muffins to cool in the tin for 5 minutes, then transfer them to a cooling rack to cool completely. Enjoy your Dark Chocolate Chunk Raspberry Crumb Muffins warm or at room temperature!
