How to Make It
In a small skillet, combine the feta and cream and simmer over moderate heat until the feta is slightly melted, about 1 minute. Stir in the softened gelatin and transfer to a blender. Puree until fairly smooth. Season with white pepper. Scrape the mixture into a shallow bowl and refrigerate until set, about 30 minutes.
Bring the feta mousse back to room temperature, about 20 minutes. Whisk the mousse until loosened. Spread the mousse in the center of each plate. Top with the tomatoes, lightly seasoning each layer with fleur de sel and black pepper. Drizzle with the olive oil, garnish with the olives, red onion and oregano and serve.