Place rack into middle of oven, and pre-heat to 180 degrees fan forced
Grease and line a large loaf tin (base measurement 25cm x 9.5cms), or a round 22cm spring form cake tin
Place chocolate into TM bowl and chop 4 seconds / speed 9, put aside, do not clean TM bowl
Place pears into TM bowl and blend 5 seconds x speed 6, scrape down sides
Add butter, sugar and eggs and mix 20 seconds x speed 4, scrape down sides
Add flours, cocoa powder, baking powder, bi-carb soda, salt and yoghurt and mix 10 seconds x speed 5
Scrape around bowl and mix another 2 seconds x speed 5
Add chocolate and fold lightly into batter, then mix 3 seconds / speed 5, scrape around bowl and repeat 3 seconds / speed 5
Pour batter into tin, level top and bake for 60 to 65 minutes, or until a skewer inserted into the centre comes out clean (it takes exactly 65 minutes in my oven whether I use a loaf tin or a round cake tin)
Rest loaf in tin for 20 minutes before removing and placing on a wire rack to cool
Ice if desired when completely cold
Keeps well at room temperature for a few days