How to make Dairy milk ganache/cake

Ingredients
Dairy milk chocolate : rs 50 to 60
Milk : 3/4 cup
Cocoa powder : 1 tbsp
Sugar : 1 tbsp
Corn flour : 1 tbsp
Butter : 1 tbsp
Nigi cakes / nigis butter cup
Karur
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Insta id: Nigi.cakes