Put graham crackers or cookies in bowl of a food processor. Blend 1 minute, or until cookies become fine crumbs (you need 2 cups).
Drizzle butter over crumbs, add salt, and pulse until combined. Press firmly into a 9-in. springform pan and bake until crumbs are set, 10 minutes.
Let cool on a wire rack.
Add 1 cup chocolate chips and 2/3 cup almonds and pulse 30 to 45 seconds, or until well chopped. In a microwave-safe bowl, heat 3/4 cup cream on full power (100%) just until bubbling.
Pour cream over chocolate-almond mixture and let sit 30 seconds; then pulse 30 seconds, or until chocolate is melted.
Pour over crust, spreading evenly, and freeze 30 minutes, or until set.
Put ice cream in the bowl of a stand mixer fitted with a paddle attachment; beat on medium speed until ice cream is smooth and malleable (like taffy), about 1 minute. Using a spatula, spread ice cream over ganache-covered crumbs. Freeze, covered, for at least 6 hours, or until ice cream is completely firm.
In a microwave-safe bowl, melt remaining 2/3 cup chocolate chips on full power until half-melted, then stir until smooth. Whip remaining 1 1/4 cups cream with the sugar and almond extract until stiff peaks form, about 4 minutes.
Run sides of pan under warm water just to loosen cake, being careful not to get water on cake.
Remove sides of pan, set cake (still on springform base) on a platter, and, with a large knife run under hot water, cut cake into 12 equal slices. Set slices on individual plates (keep any remaining cake covered in the freezer until ready to serve). Dollop almond cream onto each slice and use a spoon to drizzle warm melted chocolate over whipped cream. Chop remaining 1/3 cup toasted almonds and sprinkle over cream and chocolate.
