Start by combining the milk and butter in a small saucepan and heat over low heat until the butter has melted. Pour in a heatproof bowl or mug and set aside to cool to body temperature. In the meantime, preheat the oven to 175°C/350°F (standard oven setting) and line a 26-cm (10-inch) springform cake pan with baking parchment. I like to line both the bottom and the sides of the pan for this cake, as the parchment allows the cake to rise evenly and form less of a dome. Use a little butter to make the parchment stick to the sides of the pan.
Combine the eggs, vanilla and sugar in the bowl of a double boiler (or in a medium-sized, heatproof bowl set over a pan of simmering water) and heat, stirring, until the sugar has dissolved and the mixture has warmed to slightly above body temperature. To check whether the sugar has dissolved, rub a little bit of mixture between your thumb and forefinger. You shouldn't feel any sugar crystals.
Take the bowl off the heat and mix on high speed for ten minutes, until the mixture is pale, fluffy and can form a ribbon and the bottom of the bowl feels cool to the touch.
In a small bowl, stir together the flour, salt and baking powder. Add the dry ingredients to the egg mixture and, using a rubber spatula, stir until just combined. Give the mixture a quick whizz with the mixer. If you were to start mixing immediately after you've added the dry ingredients, you would end up with a big puff of flour in your kitchen.
Check the milk mixture to make sure it has cooled to body temperature and add it to the batter. Mix briefly until smooth.
Pour the batter into the prepared cake pan and bake for 10-15 minutes or until a toothpick inserted in the center of the cake comes out clean.
Let the cake cool for fifteen minutes in the pan, then remove from the pan and leave to cool completely on a wire rack.
Once the cake is cooling, make the syrup and prep the pan:
Combine the water and sugar in a small saucepan and heat over low heat, stirring to dissolve the sugar.
Once the sugar has completely dissolved and the syrup is clear, take the pan off the heat and pour the syrup in a mug to cool to room temperature.
Once it has cooled to room temperature, measure off 60mls (or ¼ cup) of syrup and stir in the eau de vie. Discard the rest of the syrup.
Line the springform cake pan that you used to bake the cake in with baking parchment (wash it first!). Again, use a little butter to help the parchment stick to the sides of the pan.
If your cake has formed a dome on top, carefully level the cooled cake with a serrated knife.
Place the cake back in the pan and, using a pastry brush, brush with an ample amount of raspberry syrup. Don't soak it though, you should have quite a lot of syrup left.
Wash, dry and hull the strawberries. Line the sides of the pan with halved strawberries of similar size, cut side out.
Make the mousse:
If using sheet gelatin, soak in cold water for ten minutes. If using another type of gelling agent, soak/bloom according to the manufacturer's instructions.
In a large bowl, whisk or mix together the strawberry and plain yogurts. In a small saucepan, combine the milk with the sugar and heat gently over low heat, stirring to dissolve the sugar. Once the sugar has dissolved and the milk feels hot to the touch but hasn't yet come to a boil, take the milk off the heat and add the gelatin. If using sheet gelatin, squeeze out the excess water first.
Stir to dissolve the gelatin, then add the milk mixture to the mixed yoghurt. If the gelatin doesn't dissolve, heat gently over low heat, stirring, until it does. Whisk or mix the milk mixture into the yogurt mixture until smooth.
Pour the mousse mixture into the prepared cake pan and gently rap it a few times on the counter to smooth out the top and to get rid of any air pockets. Leave to set in the fridge for at least five hours but preferably overnight.
Once the cake has set, take it out of the pan by removing the springform collar and carefully peel the baking parchment off the sides. Transfer the cake to a serving plate and decorate as desired with fresh strawberries. Serve cold out of the fridge.
Recipe by The Tough Cookie at https://thetoughcookie.com/2013/08/14/strawberry-yogurt-mousse-cake/