Directions

1. Put 150ml water, the butter and a pinch of salt into a medium pan and gently heat until the butter melts. Turn up the heat and bring to the boil. As soon as it's boiling, tip in the flour in one go. Beat quickly to combine. TIP: It's important to tip the flour in as soon as the water boils, because losing too much liquid by evaporation will affect your pastry.
2. The starch in the flour needs to be cooked out now. Beat well, over the heat, until the mix turns smooth and glossy and starts to come away from the edge of the pan. Tip the mix into a bowl and allow to cool a little.
3. Give the mixture a quick beat, then start adding the eggs a little at a time, using a whisk, wooden spoon or electric beaters. You may not need to add all the egg - stop once the pastry is smooth and elastic and drops easily off a spoon.
4. Heat oven to 220C/fan 200C/gas 7. Drop a medium nozzle into a large piping bag and scoop the pastry into it. Line two baking sheets with non-stick paper and pipe 15 x 10p-size balls of pastry onto each one. Use a wetted finger to smooth the tops. Bake for 15-20 mins until dark golden and very firm. Transfer to a rack, turn each one upside down, then leave to cool. Will keep in an airtight container for up to 2 days. TIP: The just-piped pastry buns have pointy tops, which can quickly burn. Tap them down gently with a wet finger before you put them in to bake.
5. For the sauce, heat the sugar in a large, non-stick frying pan. Melt it gently, swirling every now and again until dissolved. Turn up the heat a little, then bubble until you have a dark golden caramel, about 5 minutes in total. Keep the pan on the heat and carefully stir in the cream to make a silky sauce. Add the Cognac and stir again. Pour into a serving jug. Can be made up to 2 days ahead - warm in the microwave for a few secs and stir to loosen.
6. If making your own ice cream, place the milk and double cream in a pan. Take 1 tbsp of the sugar and add to the pan, too. Whisk the remaining sugar with the egg yolks and the seeds of the vanilla pods. Heat the milk until just boiling, then pour it onto the egg mix, whisking constantly. Tip back into the pan and heat gently, stirring with a wooden spoon until the custard thickens and coats the back of a spoon. Pour through a sieve and allow to cool. Now churn the mix in an ice-cream machine, or freeze it in a shallow container, beating thoroughly at least three times, until it is frozen and smooth. Will keep frozen for up to 1 month. Makes about 500 ml, 5 mins prep, 20 mins cooking and freezing.
7. Allow the ice cream to soften slightly in the fridge for 30 mins. Scoop into a piping bag then, holding the bag with a tea towel, poke the nozzle into the bottom of one of the buns. Pipe in the ice cream until completely filled (see tips). Work as quickly as you can - you need to get the profiteroles back in the freezer before the ice cream starts to melt. Will keep well-wrapped in the freezer for up to 1 week. NOTE: Wrapping a tea towel around the piping bag insulates the ice cream from the warmth of your hands. If piping in the ice cream seems too fiddly, simply cut the buns open with a serrated knife and fill with teaspoon-size scoops of ice cream.