Nicely done and the compound flavorings sound good. I've had to make Butter a couple of times when Whipping Cream went too far, Ooops. I added salt for flavor and it's a preservative.
A twist that has intrigued me is seeing Fermented Butter on cooking shows. The Cream is left exposed to air at room temp, until is sours and thickens naturally. I think I would want more control over the invading bacteria. 4 Tablespoons Cultured Buttermilk per Quart of Cream, rested 12 to 18 hours at room temp, makes a nicely tangy, thickened cream, aka Creme Fraiche. I'm thinking this would make for an interesting twist on regular butter...JJ