Preheat oven to 180 degree C. Butter to a baking pan and line with parchment paper. Set aside.

Take chocolate and butter in a microwave safe bowl and microwave it for 1 min.

Now set aside to cool.

Take egg, sugar, coffee and vanilla in a bowl and mix well.

Pour cooled chocolate into this and mix well.

In a separate bowl mix flour, walnuts, baking powder and salt. Pour chocolate mix into the dry ingredients and combined gently.

Spoon this into the baking pan and bake for 20 mins, now tap the pan against the oven shelf so the air escape. Now bake for 15 more mins.

Remove and cool completely.

Place in fridge for 30 mins and then slice and serve.

Slice and serve.