Preheat the oven to 170C and grease a 23cm square cake tin.
Put the chocolate and butter in a saucepan set over a low heat and gently melt, stirring occasionally. Do not overheat, the chocolate will go crumbly! Remove from the heat and cool slightly.
Whisk the eggs until thick, then gradually add the sugar and beat until glossy.
Beat in the cooled (but still warm) melted chocolate mixture, then GENTLY fold in the flour, baking powder and a pinch of salt. Do not overmix.
Pour in a little over half the brownie mixture into the prepared tin. Scatter over the raspberries, then cover with the remaining mixture.
Bake for about 40 minutes or until the surface is cooked. The brownies will be cooked when a skewer inserted into the middle comes out with just a little mixture sticking to it.
Remove from the oven, place the tin on a wire rack and allow to rest for about 15-20 minutes. Cut the brownies into squares and carefully remove them from the tin when cold.