Preheat your oven to 350°F (175°C).

Cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes. Blend in the vanilla extract, followed by the flour, cocoa powder, and salt. Stir until just combined.

Scoop portions and roll into 1-inch balls. Roll in chopped hazelnuts for coating, then place on a lined baking sheet, spaced 2 inches apart.

Press down in the center of each dough ball to create a well.

Bake for 10-12 minutes, until edges are set. Remove and cool slightly.

Fill each thumbprint with chocolate hazelnut spread, allowing warmth to slightly melt the spread.

Garnish with whole hazelnuts or a drizzle of melted chocolate. Let cool completely before serving.