Parfait means "perfect" in French, and a slice of this dreamy dessert is just that. Cream and egg whites are the base; orange-flower water, orange zest, and kumquats add layers of citrus flavor.
Line an 8 1/2-by-4 1/2-by-2 3/4-inch loaf pan with plastic wrap, allowing a 5-inch overhang; set aside. Put 3 tablespoons water into a small bowl. Sprinkle with gelatin. Let soften 7 minutes.
Heat 1/4 cup cream in a small saucepan over medium heat until warm to the touch. Pour into gelatin mixture, stirring until gelatin has dissolved. Let cool, stirring occasionally, 15 minutes.
Bring sugar, corn syrup, and 2 tablespoons water to a boil in a saucepan over medium-high heat, stirring until sugar dissolves. Cook until syrup registers 238 degrees on a candy thermometer, about 7 minutes.
Meanwhile, put egg whites and salt into the bowl of an electric mixer fitted with the whisk attachment; beat on medium speed until stiff peaks form. Reduce to medium-low speed; add syrup in a steady stream. Raise to medium-high; beat until cool, thick, and glossy. Transfer to a bowl.
Put remaining 3/4 cup cream, the buttermilk, orange zest and juice, orange-flower water, vanilla, and gelatin mixture into the clean bowl of an electric mixer fitted with the whisk attachment; beat on medium-high speed until soft peaks form. Transfer to a large bowl. Using a spatula, fold in egg whites in 2 batches. Transfer to prepared pan; smooth top. Refrigerate until set, at least 4 hours (up to overnight).
To serve, lift out parfait by overhang; cut into slices, dipping a sharp knife into warm water and wiping it dry each time. Serve with candied kumquats. Garnish with orange blossoms if desired.
The egg whites in this recipe are not fully cooked. It should not be prepared for pregnant women, babies, young children, the elderly, or anyone whose health is compromised.