Walnut

You can use a blender or a food processor to grind the rolled oats; 1 1/4 cups rolled oats yields 1 cup ground.

Each of this bombe’s layers must freeze solid before the next is added. Don’t rush the freezing time, or the layers will run together.

To remove individual Brussels sprout leaves, cut the stem out of each sprout and gently ease apart all the leaves.

The pesto can be made up to 1 hour before serving without losing its freshness; store it at room temperature.

Walnut oil can be found at most gourmet markets. Because it is more delicate than other oils, walnut oil should be refrigerated after it has been opened to keep it from going rancid.