“Lemon meringue pie, but with a buttery and crisp biscuit crust – saving you time instead of making pastry (but equally, if not more delicious!) – encasing a smooth, tart lemon filling that takes minutes to whisk up, before being baked in the oven; then topped with loads of silky Swiss meringue, with Swiss meringue ducks, too,” is how Bake Off’s Kim-Joy describes this ethereal dish.

“The Swiss meringue method takes a little more work, but the advantage is that it’s much more stable – which means the pie will keep better, as the meringue won’t weep. The meringue is also already cooked, which means the tart doesn’t need to be returned to the oven to bake further.”

Lemon meringue pie bubble bath

Ingredients:(Serves 12)

For the base:260g Biscoff biscuits (or digestives, graham crackers or ginger biscuits; or use gluten-free biscuits)120g salted butter, melted

For the lemon filling:5 medium egg yolks (reserve the egg whites for later)1 x 397g tin of full-fat sweetened condensed milk (make sure it’s full-fat!)Zest of 4 medium lemons120ml of lemon juice (from around 4 medium lemons)1⁄8tsp salt

For the meringue topping:5 medium egg whites (reserved from earlier)250g caster sugar½tsp cream of tartar

To decorate:Yellow, orange and black food dyeOr use toy ducks!

Method:

1. Preheat the oven to 180°C fan.

2. First make the biscuit base. Use a food processor to blitz the cookies to the consistency of fine breadcrumbs, or place the cookie inside a sealed plastic bag (or similar) and crush them with a rolling pin. With this quantity, it’s easiest to do this in smaller batches. Add the crumbs to a mixing bowl along with the melted butter. Mix until all the crumbs are evenly coated and the mixture resembles fine sand.

3. Tip the mixture into a 20-centimetre loose-bottomed tart tin with sides two and a half-centimetres high. Use a drinking glass (or any cup with a flat base and straight sides) to firmly pack in the crumbs, ensuring you cover the base and sides in a roughly even layer. Place on a baking tray and bake for 10 minutes, then set aside while you make the filling. After baking, reduce the oven temperature to 160°C fan.

4. Meanwhile, make the lemon filling. Add the egg yolks to a large mixing bowl and pour in the condensed milk. Whisk together until smooth and combined. Add the lemon juice and zest and salt, then whisk again until just combined. The mixture will thicken slightly as the lemon juice reacts with the condensed milk.

5. Pour the mixture over the baked base and bake for 20-25 minutes. If you gently tap the top using your finger or a spoon, it should feel firm rather than liquid-y, but still with a wobble. Place the tin on any heatproof surface, leaving the pie in the tin (don’t take it out yet) whilst it cools to room temperature, then cover and place in the fridge for at least three hours.

Tip: You can bake the lemon filling the day before and store in the fridge overnight. Then on the day you want to serve the pie, follow the recipe from step 6 onwards.

6. Just before serving, make the meringue topping. Add the egg whites and sugar to a large, heatproof bowl. Set the bowl over a pan filled with barely simmering water, ensuring the bowl does not touch the water. You want around three centimetres of water in the base of the pan. Whisk until all the sugar has dissolved (the meringue should be hot to the touch and will feel smooth and not gritty between your fingers) or the mixture reaches 70°C. Then add the cream of tartar and whisk on high speed until it is glossy and reaches stiff peaks.

7. You can decorate with toy ducks (skip to the next step, if so) or meringue ducks. To pipe the ducks, spoon a generous heaped tablespoon of meringue into a piping bag and cut a medium opening. Then place a teaspoon of meringue in a second bowl, add orange food dye and stir to combine. Transfer to a piping bag and cut a small opening. Place a large dessertspoonful of meringue in a third bowl, add the yellow food dye and stir to combine. Transfer to a piping bag and cut a large opening. You should now have three piping bags: one plain, one yellow (the largest one), and one orange (the smallest one).

8. Push the base of the tart tin upwards, allowing the sides of the tin to come away. Slide a cake lifter (or similar) underneath the tart to separate it from the base, then slide onto a serving plate. Spoon the remaining plain meringue (or all of the meringue, if not piping the ducks) over the lemon filling. Spread it all the way to the edges of the crust, then pile it higher in the centre. Using the back of the spoon, create swirls and peaks in the meringue. You can also use a blow torch to add a little bit of colour, although this is entirely optional as the meringue is already baked.

9. To decorate, finish with toy ducks, or use the piping bags to pipe your ducks onto the pie. Use the yellow meringue for the main duck body: squeeze, then gradually reduce pressure on the bag while pulling the bag away to create the larger head and tapered tail. Use the orange meringue to pipe a little beak on to each duck. Then use the white piping bag to pipe bubbles all around. Dampen the tip of your finger with a little water, then gently tap down any unwanted peaks. For the eyes, use poppy seeds or similar, or pipe them. To pipe the eyes, take a small amount of the remaining meringue and mix with black food dye. Transfer to a piping bag and cut a very small opening, then pipe on small dots. You barely need to squeeze the piping bag (if at all) – just a tiny dab is all you need.

Bake Joy: Easy And Imaginative Bakes To Bring You Happiness by Kim-Joy is published by Quadrille on August 29, priced £16.99. Photography by Ellis Parrinder