I recently made chocolate pudding by putting 25ml of cream, 410ml of 3% milk and 50ml of cornstarch (not a good way to measure cornstarch, I know) along with two handfuls of Callebaut milk chocolate into the bowl of my Kenwood Cooking Chef, set it to constant slow stir (stirring speed 1) and set the cooking temperature (this stand mixer can cook in the bowl, while mixing) to 94 deg C. After a while I reduced the stirring speed to "once in a while" slow stir (stirring speed 3).
The result was really great but I wanted to redo it with even more chocolate to get a more saturated choccy flavour.
This time, same measurements, save for the choccy, of which I put in 169g, which seemed like more than double the last time.
This time I found out the gelatinization temperature of cornstarch is 60 deg C, so I set it to cook at 70 (just to be safe). It did not thicken at all. Thinking maybe it will after refrigeration I put it in the ol' fridge but all that happened was that a very thick surface coating was created. From experience with Creme Brûlée, I think it's the fat in the chocolate that accumulated and solidified at the top.
Put it in again in the bowl, added about 100ml more of starch and set it to stir at 68 deg C.
(BTW from experiments with the same starch and water I can, indeed, confirm it gelates at ~60 deg. C)
It's still cooking but I was wondering - is there some reason adding more chocolate made it harder for the starch to gelate?