Treat cooling as a separate job

This is a cooled-and-chilled bar, not a tray to frost straight from the oven. Set up a rack and refrigerator space before mixing. Warm melted butter is suitable for the base; hot butter and a warm baked slab both create problems at later stages. Let the base become completely cool to the touch before the cream-cheese frosting goes on.

Keep the cranberries and white chocolate for the base separate from those reserved for the topping and drizzle. Small labeled bowls make those repeated ingredient names easier to follow.

Plan the triangle cuts before lifting

The written grid makes twelve rectangles, then twenty-four triangles. Mark three rows and four columns lightly before cutting all the way through the chilled slab. Use the parchment handles to lift it onto a stable board and support the base as it moves.

Wipe the knife between cuts so cranberry pieces and frosting do not drag across the next edge. Keep the bars refrigerated as the recipe requires. If only part of the tray is being served, return the remainder to cold storage instead of letting the whole slab wait out the gathering.