You can use pasteurized eggs here, but you may need to increase the whipping time in step 2 in order to get stiff peaks. Be sure to use the crisp, firm ladyfingers found in the supermarket cookie or international aisle, not the fresh, cake-like ladyfingers found in the bakery department. Twenty-four ladyfingers will weigh about 7 ounces. Do not use Whole Foods brand mascarpone for this tiramisu; the filling will be soupy. For a version without alcohol, you can substitute more coffee for the rum. Orange zest adds a pleasant floral brightness to this tiramisu; if you prefer a more traditional rendition, you can omit it. We call for an 8-inch square baking dish, but this tiramisu can also be made in eight 12-ounce serving glasses.

Whisk coffee, espresso powder, rum, and ¼ teaspoon salt in pie plate until espresso powder dissolves; set aside.

Using stand mixer fitted with whisk attachment, whip egg whites on medium-low speed until foamy, about 1 minute. Increase speed to high and whip until stiff peaks form, 1 to 3 minutes. Transfer whites to bowl.

In now-empty mixer bowl, whip egg yolks; sugar; orange zest, if using; and remaining ¼ teaspoon salt on low speed until combined, about 30 seconds. Increase speed to medium-high and whip until tripled in volume and ribbons form on top of mixture when dribbled from whisk, 3 to 5 minutes.

Add mascarpone to yolk mixture and whip on medium speed until no lumps remain, about 30 seconds, scraping down bowl as necessary. Scrape down bowl and stir by hand to ensure mixture is uniform.

Whisk one-third of whites into mascarpone mixture to lighten it. Using rubber spatula, gently fold in remaining whites until no white streaks remain. Set aside mascarpone mixture.

Combine chocolate chips and cream in 1-cup liquid measuring cup and microwave until melted and smooth, 30 to 60 seconds, stirring halfway through microwaving. Set aside.

Working with 1 ladyfinger at a time, drop 12 ladyfingers into coffee mixture; roll quickly to coat (about 3 seconds); remove; and arrange in single layer in 8-inch square baking dish, breaking ladyfingers as needed to cover bottom of dish.

Using offset spatula, spread half of mascarpone mixture (about 2 cups) on top of ladyfingers in even layer. Slowly drizzle chocolate ganache evenly over mascarpone mixture and spread into even layer using offset spatula. Repeat dipping and layering with remaining 12 ladyfingers, remaining coffee mixture, and remaining mascarpone mixture.

Using fine-mesh strainer, dust cocoa evenly over tiramisu. Cover loosely with plastic wrap (taking care not to press plastic onto surface) and refrigerate for at least 6 hours or up to 24 hours. Serve chilled.

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The Right Offset Spatula