Preheat the oven to 180°C (350°F) and line a baking sheet with parchment paper.

In a bowl, mix the flour, sugar, baking powder, and salt.

In a separate bowl, whisk together the egg, coffee, and vanilla extract.

Gradually add the wet ingredients to the dry ingredients, stirring until a dough forms.

Fold in the chocolate chunks.

On the prepared baking sheet, shape the dough into a long, flat log (about 2.5 cm thick).

Bake for 20-25 minutes until firm. Remove from the oven and let cool for 10 minutes.

Reduce the oven temperature to 150°C (300°F).

Slice the log diagonally into 1 cm thick pieces. Arrange the slices on the baking sheet, cut side down.

Bake for 10 minutes on each side until golden and crisp.

Let the biscotti cool completely before serving.