Beat the butter and sugar together for 3-4 minutes on medium-high speed.

Add vanilla and egg, beat to combine.

Sift in the flour, salt and cocoa powder.

Mix to incorporate.

Gather the dough into a ball and refrigerate for 20 minutes or up to 5 days.

Preheat oven to 375 F (190 C or 165 C with a fan).

Fill a cookie press (I use OXO) with dough and pipe cookies onto a cookie sheet (not lined with parchment paper or baking mat).

Bake for about 8 minutes.

Let the cookies cool for 3 minutes, then carefully transfer to a cooling rack to cool down completely.

Dip in chocolate and top with sprinkles (optional).

Store in an air tight container for up to 1 month.