Preheat oven to 350 degrees Fahrenheit. Spray nine-inch cake pan with nonstick spray. Line with Gefen Parchment Paper. Spray parchment. Dust with flour, tapping out any excess.

Place margarine and cocoa powder in medium bowl. Pour boiling water over; stir. Let stand two minutes; whisk until blended.

Bake cake until tester inserted into center comes out clean, about 30 minutes. Cool in pan 10 minutes. Run knife around pan edges to release cake. Invert onto rack; remove pan and parchment. Cool completely.

Whisk flour, sugar, baking soda, and coarse salt in another medium bowl.

Whisk soy milk, vinegar, egg, and vanilla in large bowl.

Gradually whisk cocoa mixture into soy milk mixture; whisk until smooth. Add flour mixture in three additions, whisking to blend between additions (batter will be thin). Pour batter into prepared pan.

Place chocolate and pareve cream in microwave-safe bowl. Heat in microwave in 15-second intervals, stirring occasionally, until melted and smooth. Stir in margarine. Let stand until spreadable, about 30 minutes.

Spread over top and sides of cake. Transfer cake to plate. Chill two hours and up to one day.

Stir brown sugar, pareve whipping cream, and margarine in heavy large saucepan over medium-high heat until margarine melts. Boil one minute without stirring. Remove from heat; whisk in sugar and vanilla. Add pecans; stir just to incorporate.

Quickly pour praline over cake. Spread just to edges (topping sets quickly). Cover with cake dome. Store at room temperature.