The first step is to prepare the mold.
Brush a layer of vegetable oil at the bottom of the mold. Cut a piece of baking paper to fit and overlap about 2-3 cm over the top edges (this will make it easy to remove when the mousse is set).
Place the piece of baking paper into the dish and cut the four corners down the sides, so they will overlap. Of course, feel free to skip this step if you wish and place the mousse directly into the dish, but it may be messy pulling it out later.
The second step is to prepare the base of the mousse cake.
Arrange the cookies on the bottom of the dish and trim to fit if needed.
The third step is to make the mousse.
Pour the lemon juice into a small bowl and sprinkle the gelatin powder over the top. It will dissolve fairly quickly, and once it has dissolved put it aside.
To make the raspberry puree, thaw the raspberries and put them into a blender, or into a tall container and use your stick blender.
Blend only until smooth.
Strain the puree through a fine sieve to get rid of the seeds. You might have to scrape the bottom of the sieve a few times to ensure it all goes through. Just look at that color!
150 grams of frozen raspberries should produce at least 70 ml of strained of puree.
Put the raspberry puree into a small saucepan (the smaller, the better myself!), and add five teaspoons of sugar. Heat gently until bubbles appear at the edge of the pot then add the lemon juice and gelatin mixture. Stir continuously to avoid lumps forming until the gelatin completely melts, which should take about 1 minute.
Put the saucepan aside to cool to room temperature. This should take about 20 minutes.
Pour the cream into a large bowl and add the other two teaspoons of sugar. Whip the cream either by hand with a whisk or in your mixer using the whisk attachment. As for the degree of whipping, personally, if it is too much, the cream begins to taste more fatty than light.
Over whipping can also quickly cause the cream to split (curdle) which is almost impossible to fix. As long as the cream has some firmness, and can maintain its shape, it is whipped enough.
Pour the cold raspberry gelatin mixture into the cream.
And gently fold it in with a silicone spatula.
Once they are mixed to a uniform pink, stop mixing. Do not over-mix.
Spoon the mousse mixture into the bottom of the mold on top of the cookies and smooth the surface with a spoon or knife.
Rinse the fresh raspberries, blot the surface, and neatly arrange on top of the cake. Although the cake is already pretty tempting now, it’s not ready to eat yet! All mousses need to set, so cover it with plastic wrap and pop it in the refrigerator for at least three hours, preferably overnight.