- Break the chocolate into a bowl, add the Stork and melt over a pan of hot water (or in a microwave on medium power).
- In a large bowl, whisk the eggs with the sugar and vanilla until creamy and slightly thickened.
- Sieve the dry ingredients and add to the eggs with the chocolate mixture and chocolate chips or nuts. Mix gently.
- Pour into a greased 22cm (9 inch) square tin.
- Bake in a preheated oven at 170°C, 160°C fan, Gas 4 for 45-55 minutes.
- Leave to cool before cutting into squares.