I made it last weekend, and I think I cooked the pastry slabs for approx 15 mins each. I read this recipe through about 20 times before I made it but I didn't read the last line which says the slice should be made the day before and rested in the fridge. I made the choux pastry the day before and the custard, and then assembled it in the morning and served for lunch at about 2pm. Still worked, and there was some leftover which tasted beautiful the next day also. Will definitely make again.