Preheat oven to 350°F and line muffin tin with 12 liners.
Prepare streusel topping by mixing all ingredients together in a bowl until evenly combined and clumpy when pressed together. Set aside.
Whisk flour, sugar cinnamon, baking powder, baking soda, and salt together in a medium bowl.
In a separate bowl, whisk together hazelnut milk, oil, vanilla, and eggs until combined.
Add liquid ingredients to dry ingredients and mix until completely smooth.
Fold in chopped hazelnuts and chocolate chips.
Divide batter among 12 muffin liners, filling each ¾ full.
Sprinkle the streusel topping over muffins.
Bake for 18-20 minutes, until a toothpick inserted into center comes out clean. Transfer muffin to a wire rack to cool before serving.
This nutritional information has been automatically calculated, and as such, may be incomplete or inaccurate. Please reference the specific ingredients you use for the most accurate nutritional information.