The night before you start, freeze your truffles in their wrappers.
The day you want to bake, pre-heat the oven to 180C.
Line 2, 25cm x 25cm tins with baking paper.
Melt the chocolates, butter and sugar together over a low heat.
Once they are melted, remove from the heat and leave to cool for 5 or 10 minutes.
Beat in each egg, one by one.
Stir in the flour.
Put enough of the batter in each of the tins to cover the base. (Probably about a quarter of the whole mixture into each of them.)
Pop 9 unwrapped truffles in each tray, spacing them evenly so you get a truffle in each bite.
Share the rest of the batter out between the two tins to cover the truffles.
Smooth out with a spatula (there will still be bit lumps where the truffles are, but just make sure they are covered with batter so they don't melt too quickly in the oven).
Bake for about 20 minutes. A skewer should come out only just clean. You could test at 17 minutes and again at 20 minutes just in case.
As always, remember that depending on your oven it could take up to 10 minutes longer, but please please try not to overcook them. Brownies are always better under-done than over.
Wait until totally cold (sorry, a pain I know) before cutting and eating.