Place the chocolate and butter in a thin-sided bowl and suspend over a gently simmering bain-marie, ensuring that the bowl does not touch the water. Melt the chocolate and stir until smooth, allow to cool slightly. Using the whisk on a hand mixer, beat the eggs and sugar until light and fluffy, stir in the melted chocolate. Combine the flour, cocoa and baking powder, mix in the nuts. Transfer the brownie mixture to the prepared tin, arrange the pears on top.
Approx. 35 mins. in the lower half of an oven preheated to 180°C. The brownies should still be a little gooey inside. Remove from the oven, allow to cool slightly. Carefully remove the tin frame, slide the brownies onto a rack and leave to cool.