Strawberry Pistachio Elderflower Mousse Cake

"Elderflowers are one of nature’s finest edible treasures that bloom during warm season. I like picking the tiny white flowers umbels to make the fragrant and sweet elderflowers cordial and just last year, I made several bottles of this flowery syrup. I allowed them to settle for all this time to enhance scents and flavors that I captured in my last new creation prepared the other week. This elderflowers, strawberry and rhubarb mousse cake has a perfect balance of sweetness and acidity and it is both chewy-crispy and creamy-fluffy."