The recipe for the Dark Chocolate Truffle center is:
1/2 Cup Heavy Cream
1/2 teaspoon vanilla
1 teaspoon brandy
3 Tablespoons Butter
Bring the cream to a boil. Remove from heat add chocolate & stir until melted. Add vanilla, brandy, & butter & thoroughly combine. Let cool in refrigerator.
Scoop chocolate with a melon baller & roll between glove covered hands gently. Place on a sheet pan lined with parchment paper and return to the refrigerator for 30 minutes.
While you could roll the ganache centers in coca powder I prefer to dip them in melted dark chocolate.