Preheat the oven to 350°F (175°C) and grease and flour a 10-inch bundt pan.

In a large bowl, combine all-purpose flour, ground hazelnuts, baking powder, baking soda, and salt.

In a separate bowl, cream the softened unsalted butter and granulated sugar until light and fluffy.

Add eggs one at a time, beating well after each addition, then mix in the vanilla extract.

Gradually mix the dry ingredients into the wet mixture, alternating with sour cream and cooled espresso, until just combined.

Pour the batter into the prepared bundt pan and bake for 45-55 minutes until a toothpick comes out clean.

Cool the cake in the pan for 15 minutes before inverting onto a wire rack.

For the glaze, heat heavy cream and butter until simmering then pour over chopped chocolate, stirring until smooth.

Drizzle the chocolate glaze over the cooled cake and sprinkle with toasted hazelnuts.