Let me just start with a word from the cookbook from whence this recipe came (Pyrex Prize Recipes circa 1953): "This is like a rich chocolate cake with a chocolate sauce underneath."
Frankly...they had me at chocolate. And if you like sweet treats, well, you're in for quite the ride. Just make sure you park a glass of milk next to your plate.
Overall, I really didn't have any hiccups with this recipe. The only thing I would mention is to make sure to either a) the milk is room temperature, or b) add the milk (and vanilla) to the melted chocolate somewhat slowly so that you temper the chocolate. I made the mistake of adding it too quickly (and it wasn't room temperature) and the chocolate seized up for a bit. But I just kept it in the saucepan until it reconstituted.
Also, you'll see the recipe calls for the Pyrex Round Cake Dish. Obviously, you don't have to have that exact one. I used a 1 1/2-quart Pyrex casserole dish (in the Snowflake pattern, mind you) and adjusted the time accordingly (baked it a little longer since it's deeper).
Taste-wise, the cake was a bit dry, so I'd probably lay off some of that sugar/brown sugar mixture next time. Since I baked it in a deeper, less-wide dish, I'm not sure enough of the boiling water got through. But I've never been one to turn down some chocolate, not matter how dry it might be. :)
Chocolate Upside-Down Pudding
6 to 8 servings
3/4 cup granulated sugar
1 1/4 cups sifted cake flour
2 teaspoons double-acting baking powder
1/4 teaspoon salt
2 tablespoons butter or margarine
1 square (1 oz.) unsweetened chocolate
1/2 cup milk
1 teaspoon vanilla extract
1/2 cup broken nuts
1/2 cup granulated sugar
1/2 cup brown sugar, well packed
2 tablespoons cocoa
1 cup boiling water
Sift together 3/4 cup granulated sugar, the flour, baking powder and salt.
Melt butter and chocolate together; mix with milk and vanilla. Stir into flour mixture. Add broken nuts and blend thoroughly. Pour into a well-greased Pyrex Round Cake Dish.
Topping: Mix together 1/2 cup granulated sugar, the brown sugar and cocoa; spread on top of batter. Pour the cup of boiling water over all. Bake.
Time: bake about 1 hour
Temperature: 350 degrees, moderate oven
Dish: Pyrex 1 1/2-quart Round Cake Dish