Crush 125g Lotus Biscoff Cookies (or graham crackers) with a food processor, or take a rolling pin to roll over the bag of cookies. Microwave 55g unsalted butter for 30 seconds, stir until melted.
Add the crushed cookies and melted butter to a bowl, stir until evenly moistened.
Line the bottom of a 7-inch springform pan with a piece of parchment paper. Transfer the cookie butter mixture to the springform pan, press firmly with the back of a spoon. Keep in the fridge.
Add 300g heavy whipping cream, 40g powdered sugar, and 2g vanilla extract to a large bowl, whip until soft peaks form. Cover the bowl with food wrap and keep in the fridge.
Prepare 2 small bowls, add 3 tbsps of cold water to EACH bowl, sprinkle 7g gelatin powder to EACH bowl. Set aside and let bloom for 5 minutes.
Add 1 cup of water to a small saucepan, bring to a boil. Keep the water simmering over low heat. Place one bowl of the bloomed gelatin to the saucepan, stir over hot water bath until dissolved.
Add melted gelatin and 150g strawberry flavor Greek yogurt to a large bowl, stir until well combined. Use a spatula to gently fold 170g whipped cream into the yogurt mixture. Optionally add 1 drop of red food coloring to the mixture to add a pink color.
Pour the pink yogurt mousse over the biscuit crust, smooth the surface with the back of a spoon. Cover the bowl with food wrap and keep in the fridge for 30 minutes.
Place the other bowl of the bloomed gelatin to the saucepan, stir over hot water bath until dissolved.
Add melted gelatin and 150g plain Greek yogurt to a large bowl, stir until well combined. Use a spatula to gently fold 170g whipped cream into the yogurt mixture.
Pour the plain yogurt mousse over the pink yogurt mousse layer, smooth the surface with the back of a spoon. Cover the bowl with food wrap and keep in the fridge for 1 hour.
Soak 15 dried edible sakura flowers in cold water for 15 minutes. Add ¼ cup of cold water to a small bowl, sprinkle 7g gelatin powder over the water. Set aside and let bloom for 5 minutes.
Add 30g diced lychee, 25g sugar, and ¾ cup of water to a small saucepan. Bring to a boil. Keep the water simmering over low heat.
Pour bloomed gelatin to the lychee sugar water, stir until dissolved. Set aside and let cool to room temperature.
Carefully pour the cooled lychee gelatin mixture over the yogurt mousse.
Place soaked sakura flowers on the top. Cover with food wrap, keep in the fridge for at least 2 hours until completely set.
Use a hairdryer to heat the sides of the springform pan until it feels warm to touch. Remove the sakura mousse cake from the mold.
Cut into 8 slices. Enjoy!