Start with cold cream cheese and room temperature softened butter.
With an electric mixer, beat cold cream cheese until smooth. With mixer running (medium speed), add room temp butter a couple of tablespoons at a time, blend each add in completely. SCRAPE BOWL with every couple of additions of butter. This helps to minimize lumps. Beat until smooth and creamy.
Add vanilla and creme fraiche (sour cream), then add powdered sugar half at a time, mixing thoroughly after each addition. Scrape down bowl after each addition. Don't overbeat which will cause mixture to get runny.
If frosting seems too soft, chill for about 30 minutes to thicken before frosting cake.
Arrange first cake layer on a cake plate or stand. Spread with frosting; place top layer on it. For 8 -inch cake top each layer with approximately 3/4 cup of frosting.
For the top and sides of the cake. Spread a thin layer of frosting on sides, called the crumb coat. This keeps the final frosting layer free of crumbs. If you have time, chill the cake to lock the crumbs in the crumb coat.
Remove chilled cake and finish frosting. To create the horizontal lines on the sides. Place cake on turntable. Place offset spatula parallel to side of cake in frosting and rotate turntable while keeping constant pressure on your spatula. Gradually lower your spatula towards the base of the cake creating a ripple effect on the sides,
Optional: Shower perimeter of cake with chocolate or multi-colored sprinkles.