Sponge Cake: Preheat the oven to 350 degrees.
In a small saucepan, warm the milk and 2 teaspoons butter together over medium-low heat.
With an electric mixer fitted with a wire whip, beat the eggs and 1 cup of the sugar on medium-high speed until the mixture is pale yellow and thick, and has tripled in volume, about 8 minutes. With the mixer on low, beat in the warm milk mixture.
Sift the flour, baking powder, and salt into a medium-size mixing bowl. Fold the flour mixture into the egg mixture and blend thoroughly until smooth. Add the vanilla and mix gently.
Grease a 17- by 12-inch baking pan or jellyroll pan with 2 teaspoons butter. Sprinkle evenly with the remaining 2 tablespoons sugar. Pour the batter into the pan, spreading it evenly. Bake until the cake springs back when touched, about 15 minutes. Cool for about 2 minutes, then gently flip it out onto a large wire rack or a large sheet of parchment paper. Let cool completely.
White Chocolate Praline Ice Cream: Combine the cream and the milk in a large heavy saucepan. Scrape the vanilla bean seeds into the cream mixture and add the bean pod. Bring to a gentle boil over medium heat.
Whisk the yolks and sugar in a medium bowl. In a slow and steady stream, whisk 1 cup of the hot cream mixture into the egg mixture. Gradually whisk the egg mixture back into the saucepan.
Add the white chocolate to the custard, and stir constantly over medium-low heat until the mixture thickens enough to coat the back of a spoon and reaches 170 degrees on an instant-read thermometer, about 5 minutes.
Strain the custard through a fine-mesh sieve into a heatproof medium bowl. Cover the mixture with plastic wrap, pressing the wrap against the surface of the custard to prevent a skin from forming. Refrigerate until well chilled, at least 2 hours.
Pour the chilled custard into an ice cream machine. Churn according to the manufacturer's instructions.
Remove from ice cream machine and fold in the broken Pecan Pralines. Place in the freezer and freeze until frozen, about 2 hours.
Pecan Pralines: In a heavy-bottomed saucepan, combine the light brown sugar, granulated sugar, heavy cream, butter, and water. Place over a medium-high heat and stir constantly until the pralines reach the softball stage, 238 to 240 degrees. Add the pecans to the candy, and pull the pan off of the stove. Continue to stir the candy vigorously with a wooden spoon until the candy cools, and the pecans remain suspended in the candy, about 2 minutes. Spoon the pralines out onto a parchment or aluminum foil lined sheet pan and cool completely before serving.
Assembly: Cut the sponge cake into 3 equal pieces to fit into the bottom of a 9- by 5- by 3-inch loaf pan. Line the loaf pan with plastic wrap, leaving an overhang over the sides. Lay 1 piece of cake flat in the pan. Sprinkle about 2 1/2 tablespoons of liqueur evenly over the cake. Spread one-third of the softened ice cream over the cake, smoothing the top with a rubber spatula and top with another cake layer. Repeat the process, working carefully to create 3 layers of cake soaked with liqueur and ice cream on top. Wrap with the plastic wrap and place in the freezer to firm up the ice cream, 1 to 2 hours.
To make the caramel sauce, in a medium, heavy saucepan, combine the sugar and water, and bring to a boil. Lower the heat to medium-low and cook, stirring occasionally, until the sugar is dissolved. Continue cooking until amber in color, about 7 minutes, swirling the pan occasionally. Remove from the heat and slowly add 3/4 cup of the cream. Return to low heat and stir until the sauce is smooth, about 1 minute. Remove from the heat and add 2 teaspoons of the almond liqueur. Let rest until cool but still liquid, about 40 minutes.
In a bowl, whip the remaining 2 cups of cream until stiff peaks start to form. Add the powdered sugar and whip into stiff peaks. Add the remaining 2 teaspoons of liqueur and whip to incorporate.
Place the frozen toffee bars in a plastic bag and smash into pieces with a mallet or rolling pin.
Remove the layered ice cream cake from the freezer. Lift from the loaf pan and remove the plastic wrap. Place the cake on a platter. Spread the whipped cream over the top and sides of the cake. Sprinkle the top and sides with the broken Heath bar pieces and drizzle the cake with the caramel sauce.
To serve, slice into 1-inch thick servings with a knife dipped in hot water.
This recipe yields 8 servings.