I suggest you don't use cocoa powder. You can go to the market and buy more than 75% dark chocolate cubes of "Kelesi" or "Swiss Lotus". After heating in water, you can add other raw materials you like, and then you can solidify yourself at natural temperature. Of course, if you want to be quick, you can put them in the refrigerator. It should be noted that the chocolate temperature should not be too high when heating in water. When it is higher than 70 degrees Celsius, the acidity of chocolate will increase.

If you insist on using cocoa powder, it is suggested that you can add cheese to the raw materials, melt the cheese by heating, stir it with cocoa powder and cool it, which will also play a certain role as a coagulant, and it can also add a better taste.