1. Preheat your oven to 375°F (190°C).

2. For the crust: In a large bowl, mix the flour and salt together. Cut in the butter until the mixture resembles coarse crumbs. Gradually add ice water, 1 tablespoon at a time, tossing with a fork until the dough holds together when pressed. Divide the dough in half and shape each into a rectangle.

3. On a lightly floured surface, roll out one rectangle to fit the bottom of a 15x10x1-inch baking pan. Transfer the dough to the pan and press onto the bottom and up the sides. Trim any excess dough hanging over the edges.

4. Bake the crust for 18-22 minutes or until golden brown. Remove from the oven and let it cool completely on a wire rack.

5. For the filling: In a large bowl, cream the softened butter and sugar until light and fluffy. Stir in the melted chocolate and vanilla extract until well combined.

6. Add the eggs, one at a time, beating well after each addition. Continue beating until the mixture is smooth and creamy.

7. Spread the filling evenly over the cooled crust. Cover and refrigerate for at least 4 hours or until set.

8. Before serving, spread whipped cream over the filling and garnish with chocolate shavings if desired.

9. Cut into squares and serve chilled. Enjoy your French silk slab pie!