Preheat oven to 210°C/190°C fan/Gas Mark 7.
To make the choux, bring the water to the boil, add in the butter and salt and heat until the butter has melted and it is at a rolling boil. Turn the heat off and immediately tip in the plain flour and beat together until smooth and coming away from the sides. Transfer to a plate and smooth out and place into the fridge to cool for 5 minutes.
Line a baking tray with baking paper and draw four circles, well spread apart with an 8cm cutter.
Once the choux mixture is cool, transfer to a stand mixer and gradually beat in the eggs until you have a firm piping consistency.
Transfer the mixture to a piping bag, fitted with a large round nozzle. Pipe four 8cm circles and then use a damp finger to smooth any spikes. Sprinkle a little water over the trays and transfer to the oven and bake for 25 minutes until puffed and golden.
Meanwhile, whisk the royal icing and egg white until smooth and a thick piping consistency. Add in the food colouring and mix until bright pink. Place in a piping bag fitted with a medium nozzle. Set aside.
Once the chouxnuts are baked, remove from the oven and turn upside down. Poke four evenly spaced holes in the bottom of each with a cocktail stick. Allow to cool, bottom side up, on a wire rack for 5 minutes.
To make the cream, mix the cookie butter with 50ml of cream until well combined and then add in the remaining cream and beat to soft peaks. Transfer to a piping bag with a small nozzle.
Once the chouxnuts are cool, use a cocktail stick to make the holes in the bottom of the chouxnuts large enough for the cream piping nozzle and then fill the chouxnuts equally with the cookie butter cream. Turn upright onto a wire rack.
To decorate, pipe a wide wobbled circle around the top to look like an iced doughnut. You can build up the line depth gradually so it doesn’t dribble down the sides. Once piped, top with the sprinkles and serve.