This is a light-colored but rich and creamy chocolate filling. This fills a 17 ½ × 11 ½-inch jelly-roll generously. If you whip it until it is too stiff, warm the spatula with hot water to help in spreading. Start this a few hours in advance of when it is needed. For a Mocha Ganache Filling, add 2 teaspoons instant espresso or coffee powder to the cream, and use bittersweet, semisweet, or milk chocolate.

Bring to a boil in a medium saucepan:

Remove from the heat and whisk in:

Cover and let stand for 10 minutes. With a silicone spatula, stir the mixture until perfectly smooth, scraping the bottom of the pan to be sure all the chocolate is melted. Cover and chill for at least 2 hours. (The ganache can be refrigerated for up to 5 days or frozen for up to 6 months.) To use, in a large bowl, or in a stand mixer with the paddle attachment, beat on low to medium speed just until the ganache is thickened and begins to hold a shape; do not overbeat (this happens very quickly if using semisweet or bittersweet chocolate, so watch it carefully). Use immediately.