Dissolve 1 tablespoon of instant coffee in 2 tablespoons of hot water in a small bowl. Stir well until fully dissolved and allow to cool.

In a large mixing bowl, beat 1 stick of softened unsalted butter and 1 cup of icing sugar together using an electric mixer for 2-3 minutes until fluffy.

Add 1 large beaten egg to the mixture and mix on medium speed until fully incorporated, about 30 seconds.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of cornstarch, and 1 teaspoon of ground cinnamon.

Fold the cooled coffee mixture into the butter and sugar, then add the dry ingredients gradually, mixing until just combined.

Transfer the cookie dough to a piping bag fitted with a large star tip, pipe onto a lined baking tray, spacing them about 2 inches apart.

Chill the piped cookies in the freezer for 5 to 10 minutes to maintain their shape while baking.

Preheat your oven to 350°F (175°C) and bake the cookies for about 8 minutes or until edges are lightly golden.

Cool baked cookies on a wire rack, then dip in melted dark chocolate and sprinkle with chopped pistachios.