Pistachio Mousse (creme mousseline)
Try it in a fraisier cake.
Shell pistachios and remove skins. If pistachios are not already roasted, toast them in a 300F oven for 10 minutes. Immediately process with oil until completely smooth. Set aside or refrigerate.
Bring the milk, vanilla bean and seeds, and half the sugar to a boil over medium heat. Meanwhile, whisk the remaining sugar into the yolks. Add flour and cornstarch to the yolks and whisk to blend. Slowly pour the milk into the yolks, whisking on high speed constantly.
Return the mixture to the pot, and cook over medium-high heat, whisking fast, thoroughly, and constantly, until it thickens rather dramatically, about 2 minutes. Off heat. Whisk in half the butter. Place the mixture in the refrigerator until it comes to 65F, about 10 minutes, removing once to whisk. Whisk on high for 1 minute, then whisk in remaining butter. Continue whisking on high speed for 5 minutes.
Slowly whisk in pistachio. Add green food coloring to make the color appealing. Set aside or refrigerate.