This is not exactly what you described but seems to be very good.

Ho-Ho's Cake
Source: Mam-ma
Serves/Makes:12 servings

1 box german chocolate cake mix made according to package directions
Filling:
3 tbsp (45 ml) flour
1 1/4 cups (300 ml) milk
1/2 cup (125 ml) margarine
1 1/2 cups (350 ml) white sugar
1/2 cup (125 ml) Crisco or other vegetable shortening

Icing:
1/2 cup (125 ml) margarine
1 egg
1 tsp (5 ml) vanilla
2 tsp (10 ml) hot water
2 cups (475 ml) powdered sugar
cocoa (to suit taste)

Bake cake according to directions on box in greased 9 x 13-inch pan.

Filling:
Cook until thick, flour and milk. Cool completely. Cream sugar, margarine and Crisco.
Add to milk mixture. Beat until fluffy. Let cool in refrigerator. Put on cake and freeze.

Icing:
Beat all ingredients together and spread on filling. Keep refrigerated.

Comments:
The icing contains a raw egg. If you do not want to use this, just make a regular chocolate powdered sugar icing as a substitute.