Almost Zippy's Chantilly Frosting

Growing up in Hawaii one of my favorite desserts is Chantilly cake from Zippy's Napoleon Bakery! With a father who was in the military, I wasn't able to live in Hawaii for my entire childhood. But every time we went home to visit one of the first things I'd want to do is to go and eat some Chantilly cake from Zippy's. The beach was great but I really just wanted some cake!
The reason the cake is so good is because of the frosting, it's a lot like German chocolate frosting but tastes almost like buttery caramel, it's really hard to describe which is why it has been just as difficult to duplicate. But I think I've pretty much figured it out! So here it is, I hope those who have moved from the islands can satisfy your Chantilly cake cravings and those who have never tasted it can now have something new to crave with this recipe.

**I came up with a much easier recipe here.

This will make enough frosting to frost a 9x13 cake or two 8" layers. The consistency doesn't work too well for cupcakes.

Ingredients:
-1 C. fully fatted evaporated milk
-1 C. white sugar
-1/2 C. brown sugar
-1 t. cornstarch
-3 egg yolks, beaten
-1/2 C. butter
-1 t. vanilla extract

optional:
-1 C. chopped macadamia nuts

Directions:
1) Combine milk, sugar, cornstarch, egg yolks, butter, and vanilla in the top portion of a double boiler. (or in a metal bowl placed over a saucepan of boiling water).
2) Cook mixture over a medium heat until it is thick, about 12 minutes. Stir it constantly to keep from clumping and the eggs from scrambling.
3) Remove from heat.
4) Add nuts if you desire.
5) Stir occasionally until it is thick enough to spread.

Enjoy! And for those of you who have tasted Zippy's Chantilly cake I'd love to hear what you think, am I close?

**I came up with a much easier recipe here.