Old Fashioned Chocolate Pie

I have a lot of cookbooks. I guess you could say I collect them. About once a week I pluck one off the shelf hoping to discover a new recipe I'd like to make. Last week I found this pie recipe in one of my Taste of Home cookbooks. My husband claims it's the best dessert I've ever made. I don't quite agree, but it is tasty and definitely a keeper.

1 cup sugar
1/3 cup baking cocoa
1/4 cup all-purpose flour
Pinch salt
2-1/4 cups water
1 Tbsp butter
1 tsp vanilla extract
1 pastry shell (9 inches), baked (I'm a fan of Pillsbury pie crust in the refrigerated section that you roll out and bake in a glass pie plate.)
Whipped cream

In a large saucepan, combine sugar, cocoa, flour and salt; gradually add water. Cook and stir over medium heat until mixture comes to a boil. Continue cooking and stirring for several minutes until thickened. Remove from heat; stir in butter and vanilla.

Pour into pastry shell. Let pie cool for a bit, then cover and refrigerate for 2-3 hours before serving. Garnish each slice with whipped cream.