Heat oven to 180C/160C fan/gas 4.
Line a 20 x 30cm baking tray tin with
baking parchment. Put the chocolate,
butter and sugar in a pan and gently
melt, stirring occasionally with a
wooden spoon. Remove from the heat.
Stir the eggs, one by one, into the
melted chocolate mixture. Sieve over
the flour and cocoa, and stir in. Stir
in half the raspberries, scrape into the
tray, then scatter over the remaining
raspberries. Bake on the middle shelf
for 30 mins or, if you prefer a firmer
texture, for 5 mins more. Cool before
slicing into squares. Store in an airtight
container for up to 3 days.