Heat oven to 180/gas 4
Line baking tin with greaseproof paper
Break 250g dark chocolate into pieces, put into glass bowl with 175g butter/marg and melt in microwave (Other melting techniques are available).
Mix 3 eggs, 250g sugar, 1 teaspoon vanilla extract and 150g plain flour in a larger bowl.
Then add melted chocolate/butter and stir again.
Finally, stir in 100g chocolate chips.
Bake in oven for half an hour.
If you can, let it cool before cutting up and eating. Makes about 24 pieces.
*Can use white chocolate/chocolate chips instead if you desire, but this is very sweet.