Combine egg yolk, sake, and yuzu juice in a heat proof bowl or the top of a double boiler and set over barely simmering water. Using a whisk, beat until pale, light and thick, for about 3 minutes. Whisking constantly, slowly drizzle in clarified butter until mixture is thick. Fold in yuzu peel and whipped cream.
Add butter and olive oil to a large fry pan over medium heat. Saute vegetables for 2 minutes and add vegetable stock. Continue to cook until vegetables are heated through and nicely glazed. Season with salt and freshly ground white pepper.
Divide vegetables among 4 large bowls and top with yuzu mousseline. Serve immediately.