Ingredients
Method
Butter Biscuit Base
- Preheat the oven to 350˚F (175˚C). Line a baking sheet with parchment paper, a silicone baking mat, or a perforated baking mat.
- Using a stand mixer fitted with the paddle attachment or a hand mixer with a medium bowl, cream together the 95 g unsalted butter, 65 g granulated sugar, and 65 g light brown sugar until light and fluffy (about 3 minutes). Add 1 large egg and beat on medium speed until completely incorporated.
- In a medium bowl whisk together 165 g all-purpose flour, ½ tsp baking soda, and ½ tsp fine sea salt. With the mixer on low, gradually add the dry ingredients about a tablespoon at a time.
- Put about half of the dough on a sheet of parchment paper, and place a second sheet on top. Roll the dough to about ¼" thick. Peel the top piece of parchment paper off, then place it back on and flip the dough over to peel the other piece of parchment off (this makes it much easier to remove the cookies after cutting them out). If the dough feels soft at this point, place the dough sandwiched between both sheets of parchment paper on a baking sheet and pop it in the freezer for 10-20 minutes to firm up.
- Using a cookie cutter that's about ¼–½" smaller than the molds you will be using, stamp out as many shapes as you can. Carefully transfer them to the baking sheet leaving 1" between each cookie. Bake for 8–10 minutes or until just slightly golden.
- Leave to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. This recipe makes enough for 3–4 batches of mini mousse cakes—you can either bake the whole batch and freeze the extra cookies to use as bases ready to assemble in mousse cakes later or just eat them as they are! You can also freeze the raw dough tightly wrapped to roll out and bake fresh another day. It would be difficult to properly cream less butter, so I don't recommend making a smaller batch.
Berry Purée
- Add 365 g berries 40 g granulated sugar, and 2 ½ tsp lemon juice to a small saucepan. Cook over medium heat while stirring occasionally and mashing the berries with your spoon or spatula until they've softened, lost most of their juices, and the mixture has slightly thickened and looks like a loose jam.
- Carefully pour the berry mixture into a blender or food processor. Make sure your blender or food processor can handle hot liquids, otherwise allow the berry mixture to cool for 10–15 minutes first. Blend until a smooth as possible, then pass the mixture through a sieve into a bowl to remove the skins and seeds.
- Measure out ½ cup to use for the Berry Gelée, and store the rest in the fridge to use for the Berry Mousse later.
Berry Gelée
- Line a small baking sheet with a silicone or teflon mat. Sprinkle 1 ½ tsp powdered gelatin over 2 tbsp cold water and allow to bloom (i.e. absorb the water and swell up) for about 5–10 minutes.
- If the ½ cup Berry Purée is still warm, stir the bloomed gelatin into it until melted and smooth—otherwise, microwave the bloomed gelatin for 10–15 seconds just until melted, then stir it into the berry purée.
- Pour the mixture out onto the prepared baking sheet and tilt it around until evenly spread (it does not need to reach the edges, aiming for a thickness of about ¼". Place in the fridge or freezer until completely set.
- Remove from the fridge. Place another silicone or Teflon mat on top of the gelée and flip it over, then peel the other silicon or Teflon mat off. Using a cookie cutter that's at least 1" smaller than the molds you will be using, stamp out as many shapes as you can. If you're kitchen is very warm, you may want to store the cut out shapes in your fridge until you're ready to assemble the mousse cakes, otherwise your gelée may start to soften.
Berry Mousse
- Sprinkle 1 ½ tsp powdered gelatin over 2 tbsp cold water and leave to bloom for 5–10 minutes. Meanwhile, whip 1 cup heavy whipping cream to stiff peaks.
- Microwave the gelatin for 10–15 seconds, just until melted. Stir into the remaining Berry Purée. Pour the berry and gelatin mixture over the whipped cream, and gently fold in until incorporated.
White Chocolate Ganache
- Add 50 g white chocolate to a heat-proof and microwave-safe bowl. Heat 50 g heavy whipping cream in a small saucepan or in the microwave just until steaming. Pour over the chocolate and let sit for 1–2 minutes to allow the chocolate to melt. Whisk until smooth. If any chocolate refuses to melt, microwave for 15–30 seconds and whisk again.
- Cover with plastic wrap and refrigerate until chilled and set, about 2 hours.
- Line a small baking sheet with parchment paper or a silicone mat. Transfer to a disposable piping bag and snip an opening about ¼" wide, and pipe shapes that are similar to the shape of the molds you will be using, and about 1" smaller. Or alternatively, pipe them into silicone molds that are smaller than the molds you will be using for the mousse cakes. Freeze until solid, about 1 hour (in the video, I pipe the ganache directly into the mousse, but it ended up sinking towards the bottom of the mold—freezing the ganache first will work much better!)
Matcha Mousse
- Add 160 g whole milk and 1 tbsp lemon zest to a microwave-safe bowl. Microwave for about 30 seconds, or until the milk is steaming. Allow to infuse for 10 minutes, then pour through a strainer into a clean bowl to remove the zest. Whisk in 2 tsp matcha until smooth.
- Sprinkle 1 ½ tsp powdered gelatin over 2 tbsp water and leave to bloom for 5–10 minutes. Microwave for 10–15 seconds or just until melted, then whisk into the milk and matcha mixture.
- Whip 1 cup heavy whipping cream to stiff peaks, then fold in the milk and matcha mixture until combined.
Assemble
- Spoon some mousse into each mold until it's about halfway full. Smooth the mousse up the sides of each mold, and add another spoonful of mousse. For a berry mousse cake add a gelée shape in the middle (you can stack 2–3 on top of each other if you want a thicker layer of gelée). For a matcha cake add a piece of frozen white chocolate ganache. Top it off with a butter biscuit. Ideally, the biscuit base will be flush with the tops of the molds—if not, fill the mold with more mousse next time and for now, just add some more mousse to fill the mold. Use an offset spatula to even out the mousse.
- Freeze for at least 8 hours or ideally overnight. Remove from the mold while still frozen, then leave in the fridge to defrost, then 20 minutes before serving remove them from the fridge to allow them to come to room temperature.