Preheat oven to 350 degrees.
Place 3 of chocolate squares and the butter in a large microwaveable bowl. Microwave on "high" for 2 minutes; stir until chocolate is completely melted.
Mix in sugar and vanilla. Add eggs, one at a time, beating with a mixer on low speed after each addition.
Add .25 cups of the flour and the baking soda, mix well. Add remaining 1 cup flour alternating with the water, beating well after each addition.
Pour evenly into 9-inch round cake pan sprayed lightly with cooking spray.
Bake 30 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pan. Cool completely.
Top with whipped topping and strawberries just before serving. Melt remaining 2 chocolate square as directed on package. Drizzle over cake top. Let stand until chocolate is set.