Nutella needs to be refrigerated for at least 2 hours before using. Cookies can be made up to one week ahead. Store in an airtight container.
150g unsalted butter, chopped, at room temperature
1⁄2 cup brown sugar, firmly packed
1⁄3 cup caster sugar
1 tsp vanilla extract
1⁄2 cup hazelnut meal
11⁄4 cups plain flour
1/3 cup cocoa powder
1⁄2 tsp baking powder
1⁄2 cup Nutella, chilled
Grease and line two large oven trays with baking paper.
2 Beat butter, sugars and vanilla in a small bowl of an electric mixer until light and fluffy. Add egg. Beat until combined. Transfer to a large bowl.
3 Add hazelnut meal and combined sifted our, cocoa and baking powder. Mix well.
4 Roll two level tblsps of dough into a ball. Using your thumb, make an indent into dough. Place on prepared tray, indent-side up. Repeat with the remaining dough, placing about 5cm apart on prepared trays.
5 One at a time, spoon a heaped tsp of chilled Nutella into each indent. Pinch dough together to enclose. Re-roll into balls. Return to trays.
6 Cook in a moderate oven (180C), swapping trays halfway through, for about 12 minutes, or until firm when lightly touched. Remove from oven. Cool completely on trays.