To prepare the cupcake batter:
1) In a large heat resistant bowl, combine the chocolate chips and butter over a pan of simmering water, without letting the bottom touch the water. Stir gently until the chocolate and butter are melted and combined. You may use a microwave, if preferable.
2) Remove the chocolate from the heat and stir in the vanilla. Add the sugar. Beat with a handheld electric mixture until smooth and combined, about 3 minutes. Add the eggs, 1 at a time, mixing for 20 seconds between each egg to incorporate.
3) In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt. Mix until well blended.
4) Using ladle or small measuring cup, 2/3 fill the cake papers and place a peanut butter cup in the centre of each cup, pressing down slightly. Bake for about 20 minutes, until the cakes are firm to the touch.
To prepare the frosting:
1) Using a handheld electric beater, cream the cream cheese and butter together thoroughly. Add the chilli power and cinnamon, mixing to incorporate. Add the salt, vanilla, and icing sugar. Finally, mix in the melted chocolate and blend thoroughly until smooth. If additional thickening is needed, add more sifted icing sugar, a little at a time, until a spreadable consistency is reached.