In a food processor, grind the hazelnuts until finely ground.
In a large bowl, sift the flour, salt and baking powder together.
In a medium bowl, add the sugar and butter and mix together until smooth and lightened.
Add the eggs, milk and vanilla, beat until will combined.
Add the wet ingredients to the flour mixture, stirring to combine.
Fold in the ground hazelnuts.
Pour the batter into the springform pan, tapping to release any bubbles and gently smooth the top.
Bake for 45 to 60 minutes, checking with a cake tester or toothpick after 45 minutes.
Cool on a wire rack before removing the springform pan.
Mix the chocolate glaze by adding the powdered sugar, cacao, vanilla, nutmeg and cream into a small bowl.
Whisk until smooth then frost the cake with a spatula.
Notes
I modified this recipe from MyDinner.co.uk, adjusting it for Imperial measurements, adding the chocolate glaze and tweaking the base recipe slightly (adding vanilla primarily).