Heat oven to 350ºF. Grease 3 6-by-2-inch round cake pans and line the bottoms with parchment. Spread 2 cups cake batter in each pan (bake remaining batter as desired for another use). Bake until cakes spring back when touched, about 35 min. Cool completely.
Trim the domed tops of cakes. Place one cake on a serving platter and top with ⅔ cup frosting. Repeat for next two layers. Cover cake in plastic wrap and chill before frosting the entire outside.
Measure pretzel rods against the side of the cake and trim them with a serrated knife to hit just above the top of the filled cake. Melt the white candy coating disks. Dip the cut ends of the pretzels in white candy and coat almost all the way up the rod. Place on a parchment-lined baking sheet to set.
Melt pink candy coating disks. Mix remaining white coating with half the pink coating to make some of it light pink. Drizzle both light and dark pinks over the dipped pretzels. Let set at room temperature or in the fridge.
Frost the outside of the cake, smoothing the sides and top. Place pretzels around the outside.
To make pink coating curls and shards, remelt any remaining pink coating. Spread in a thin layer, about ⅛ inch thick, on the back of a clean baking sheet. Chill in fridge until solid, about 5 min. Using the back of a flat metal spatula or bench scraper, make shards by scraping the coating. Top cake with the curls and shards.
An impressive centerpiece that will stop the show!