Brown Sugar Crust:
2 sticks unsalted butter, softened
1 1/2 cups packed light brown sugar
1 egg, separated
2 cups flour
1/8 teaspoon salt
For Praline Topping:
1 cup packed light brown sugar
2 tablespoons sugar
1/4 cup dark corn syrup
1 stick unsalted butter
1/4 cup whipping cream
2 cups chopped pecans
2 tablespoons bourbon
1 tablespoon vanilla
pinch of salt
1 1/2 ounces bittersweet chocolate, chopped (about 1/4 cup) melted
Heat oven to 350 degrees. For crust, cream butter and sugar, until light and fluffy, with a mixer on medium speed. Add egg yolk. Beat well. Add flour and salt; mix until smooth. Transfer to 13x9x2 inch baking pan; spread evenly with spatula. Cover with plastic wrap; press gently into place. Remove plastic.
Whisk egg white until foamy; brush lightly over dough with a brush. (Some will be left over.) Bake until puffed and lightly browned, about 20 minutes. Transfer to rack; let rest 15 minutes.
For praline topping, heat sugars, corn syrup and butter to boil in small, heavy saucepan over medium-low heat, stirring frequently. Let boil 1 minute. Add cream; stir until smooth. Stir in pecans, bourbon, vanilla and salt. Pour filling over crust; tilt pan to spread evenly.
Bake until topping is dark brown and bubbly (bubbles will be large at first, then smaller and closer together), about 25 minutes. Cool completely; cut into squares. Use a fork to drizzle melted chocolate over surface. May take several hours for praline to firm up completely. (Can be baked 2 days ahead and kept at room temperature in airtight container, each layer separated by waxed paper.) Can be served with ice cream for a plated dessert.
