All Purpose Chocolate Sauce

I use this recipe for chocolate sauce in almost all of my chocolate desserts: soft chocolate cake, chocolate macaroon etc.

the ingredients are divided in to 3 parts

1st part:
cocoa powder 30g
agar powder (ผงวุ้น) 1/2t
sugar 60g
milk 100g
whipping cream 150g
evaporated milk 100g
2nd part:
evaporated milk 100g
corn starch 30g
3rd part:
butter 50g

1) in a sauce pan: mix all of the 1st part ingredients together.

2) gradually stir it with hand mixer over low heat, you have to be really patient when doing this part. pls dont stop stirring it!

3) a small cup stir the second part of the ingredients together

4) about 10-15min, when the sauce start to bubble,add in the second part of the ingredients and stir it fastly till it is nice and thick then remove the sauce pan from the heat

5) add in the 3rd part of the ingredients when the sauce is still hot. stir in the butter well
6) store the sauce in the fridge till it is cold before using it.