- Nonstick vegetable oil spray
- 1/3 cup all purpose flour
- 1/2 teaspoon ground cinnamon
- 1/4 teaspoon baking powder
- Pinch of salt
- 6 tablespoons (3/4 stick) unsalted butter, cut into 4 pieces
- 1/3 cup natural unsweetened cocoa powder
- 3/4 cup sugar
- 1 large egg
- 1/2 teaspoon vanilla extract
- 12 ounces bittersweet chocolate (do not exceed 61% cacao), chopped
- 2 3/4 cups half and half, divided
- 6 large egg yolks
- 2/3 cup sugar
- 1/2 teaspoon ground cinnamon
- Pinch of salt
- 4 large egg whites, room temperature
- 1/2 teaspoon cream of tartar
- Pinch of salt
- 1/2 cup sugar
- 2 teaspoons finely grated orange peel
- 9-inch-diameter springform pan with 3-inch-high sides
- Candy thermometer
- Ice cream maker
- Kitchen torch
- Soften about 6 cups of purchased chocolate ice cream. Mix in 1/2 teaspoon cinnamon. Spoon the ice cream over the baked brownie layer, freeze, and continue with the recipe.
- Preheat oven to 325°F. Line inside of 9-inch-diameter springform pan with 3-inch-high sides with foil. Coat lightly with nonstick spray. Whisk flour and next 3 ingredients in small bowl. Melt butter in medium saucepan over medium low heat. Remove from heat; whisk in cocoa powder, then sugar. If batter is still hot, let cool. Whisk in egg and vanilla, then flour mixture. Spread batter over bottom of pan.
- Bake brownie layer until tester inserted into center comes out with a few moist crumbs attached, 15 to 17 minutes. Cool in pan on rack. Cover and freeze.
- Stir chocolate and 1 1/2 cups half and half in medium saucepan over medium heat until chocolate is melted, stirring often. Remove from heat. Whisk egg yolks and next 3 ingredients in medium bowl. Gradually whisk in hot chocolate mixture; return to saucepan. Cook over medium-low heat until mixture leaves path on back of spoon when finger is drawn across and custard registers 170°F to 175°F on candy thermometer, stirring constantly, 6 to 8 minutes.
- Strain custard into another medium bowl. Add remaining 1 1/4 cups half and half. Refrigerate until cold, about 3 hours.
- Process custard in ice cream maker. Transfer to pan; spread evenly over brownie layer. Cover; freeze overnight. DO AHEAD: Can be made 3 days ahead. Keep frozen.
- Using electric mixer, beat egg whites in large bowl until foamy. Add cream of tartar and pinch of salt. Beat until soft peaks form. With mixer running, gradually add sugar. Continue to beat until meringue forms stiff glossy peaks. Beat in orange peel. Spread over ice cream layer. Using spatula or back of spoon, swirl decoratively, forming peaks. Freeze until firm, at least 3 hours. DO AHEAD: Can be made 1 day ahead. Cover and keep frozen.
- Remove cake from freezer. Release pan sides; remove foil. Transfer cake to plate. Using kitchen torch, brown meringue or place under broiler 1 to 2 minutes to brown.