Preheat the oven to 400°F (200°C) and line a muffin tin with paper liners.

Toast the walnuts on a baking sheet for 7-8 minutes until golden and fragrant.

In a large bowl, sift together the all-purpose flour, baking powder, cinnamon, nutmeg, and salt.

Cream together the brown sugar and butter in a separate bowl until light and fluffy.

Add the eggs, maple syrup, milk, maple extract, and vanilla extract to the creamed mixture and mix well.

Gradually add the dry ingredients to the wet mixture and fold in the toasted walnuts.

Spoon the muffin batter into the liners, filling them about three-quarters full.

In a small bowl, mix flour, brown and white sugars, butter, walnuts, cinnamon, and hazelnut extract for the topping.

Bake for 5 minutes at 400°F, then reduce to 375°F (190°C) for 16-17 more minutes.

Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack.

Whisk together icing sugar, milk, maple syrup, and maple extract for the glaze and drizzle it over the cooled muffins.