2) For the mousse, whisk together the 3 whole eggs, 3 egg yolks, 250g sugar, lemon zest, lemon juice and a pinch of salt in a large heat-proof bowl. Place the bowl over a pan of simmering water and cook, stirring constantly with a wooden spoon, for about 10 to 12 minutes until the mixture is thick. When mixture thickens, stir with a whisk if desired.
3) Take off the heat and set aside for 15 minutes. Cover with cling film directly on the surface to stop it forming skin. Refrigerate for 1 to 2 hours, until completely chilled.
4) Place half the *egg whites and a pinch of salt in the bowl of an electric mixer fitted with the whisk attachment. Beat on high speed. Add the remaining 2 tbsp of granulated sugar and continue to beat until the whites are stiff and shiny.
5) Carefully fold the beaten whites into the cold lemon mixture with a rubber spatula. Place the double cream in the same bowl of the electric mixer fitted with the whisk attachment (no need to clean the bowl) and beat on high speed until the cream forms stiff peaks. Carefully fold into the lemon mixture. Fold in the lemon curd, and pour into a 20cm-diameter, 7.5cm-deep souffle dish.
6) Decorate the top with sweetened whipped cream and lemon slices that have been cut into quarters. Chill and serve cold.
*Raw egg warning
Food Network Kitchens suggest caution in consuming raw and lightly-cooked eggs due to the slight risk of salmonella or other food-borne illness. To reduce this risk, we recommend you use only fresh, properly-refrigerated, clean, eggs with intact shells, and avoid contact between the yolks or whites and the outside of the shell.