Step 1

Line the bottom and sides of a 9x5-inch loaf pan with plastic wrap, allowing 4 to 5 inches to extend over all sides.

Step 2

Stir cookie crumbs and almonds together in a bowl. Set aside.

Step 3

Place chopped bittersweet and semisweet chocolate in a large bowl and set a fine wire-mesh strainer over the bowl; set aside.

Step 4

Whisk eggs, sugar, and salt together in a medium bowl until well combined.

Step 5

Heat 1/2 cup cream and water in a small saucepan over medium heat until mixture begins to simmer, 3 to 4 minutes. Slowly whisk hot cream mixture into egg mixture until completely combined. Return mixture to the saucepan and attach a candy thermometer to the pan. Cook over medium-low heat, stirring constantly with a rubber spatula and scraping the bottom of the pan, until mixture is slightly thickened and registers 160 to 165 degrees F (70 to 74 degrees C), 4 to 5 minutes. Do not let mixture simmer.

Step 6

Immediately pour into the strainer over the chocolate. Discard any solids left in the strainer. Let chocolate mixture stand for 5 minutes. Whisk until chocolate is melted and smooth; whisk in vanilla and almond extracts. Let stand until completely cool, about 15 minutes.

Step 7

Beat remaining 1 1/2 cups cream with an electric stand mixer, using the whisk attachment, on medium-high speed until soft peaks form, 1 1/2 to 2 minutes.

Step 8

Whisk 1/3 of whipped cream into chocolate mixture until completely combined. Gently fold remaining whipped cream into the chocolate mixture using a rubber spatula until incorporated and no streaks of whipped cream remain. Spoon mixture into the prepared pan and smooth evenly with a small offset spatula. Sprinkle evenly with cookie crumb mixture.

Step 9

Pull excess plastic wrap at sides tightly over cake, gently pressing down on cookie crumb mixture. Freeze, 12 to 24 hours.

Step 10

Lift semifreddo from pan, using plastic wrap as handles, and transfer to a serving plate. Let stand for 15 minutes. Cut semifreddo into 8 slices, using a serrated knife dipped in hot water and wiped dry after each slice.