1Mix all the ingredients except the chocolate chips in a large bowl with an electric mixer for about 3 minutes. Stir in the chocolate chips.
Pour batter in a 12 cup Bundt cake pan already buttered.
2Bake in a preheated oven at 325 for about an hour and 10 minutes.
Let the cake cool down at least 20 minutes before flipping onto a cake plate.
3In a large bowl with a mixer cream the butter, shortening, sugar and vanilla at least 5 minutes in order to dissolve the sugar. Do not loose patience.
Stir corn starch in milk and cook until it thickens.
Cool about 10 minutes and then little by little add it to the butter mixture. Beat at low speed until creamy and well blended.
The icing will appear curdled at first, but continue beating it well until it becomes smooth.