In saucepan over low heat, melt margarine or butter, then stir in chocolate. (This will greatly reduce the chance of scorching the chocolate. Mixture may look separated but it will come together after cooking with egg yolks.)
Separate eggs, reserving yolks in mixing bowl and retaining whites in separate container. Whip yolks on medium-high speed until they turn pale yellow. Slightly warm egg yolks by slowing adding 1 to 1 1/2 cups of chocolate-margarine mixture while mixer is running on medium-high speed.
Return this mixture to remaining chocolate/margarine mixture, stirring constantly with rubber spatula as it cooks over low heat until mixture thickens, about 3 minutes.
Remove from heat and immediately pour into large mixing bowl to speed up cooling. Add powdered sugar, vanilla extract and almonds; mix well with wire whisk. Allow to cool to room temperature.
Place chocolate wafers in plastic bag and roll into fine crumbs using rolling pin. Pour into separate bowl and add melted butter. Mix thoroughly with wire whisk, until moist and crumbly. Reserve 1 cup of crumb mixture for final step.
Spread remaining crumb mixture in even layer across bottom of 13 x 9-inch baking pan, gently pressing down. (If crumb mixture is not pressed, it will fall apart during cutting.) Set aside.
Whip egg whites in clean and chilled bowl until whites are stuff but not dry, just holding a soft peak. Using rubber spatula, gently fold all egg whites at once into chocolate/margarine mixture. Be sure to mix almonds thoroughly since they tend to sink to bottom of mixture.
Spread half of chocolate filling, about 1 quart, evenly over bottom crust. Add overflowing scoops of coffee ice cream on top of chocolate filling. Place 4 scoops across by 6 scoops down. Work quickly to prevent ice cream from overly melting.
Pour remaining chocolate filling over ice cream. Smooth top with rubber spatula. Surface will be slightly bumpy.
Sprinkle reserved crumb mixture evenly over top of pie. Cover with plastic wrap. Place in freezer on flat surface to ensure even freezing, at least 8 hours.
To cut, dip chef's knife into hot water and pull knife through the pie. Re-dip in hot water after each cut. To serve, top each piece with hot fudge sauce and garnish with toasted almond slices.