Position a rack in the center of the oven and preheat to 375 degrees F. Line twelve 2 ½ inch muffin cups with paper liners. Place cocoa in a small bowl and stir in ½ cup very hot tap water to dissolve.
In a large bowl combine the melted butter and sugar beat with an electric mixer until blended. Add the egg and beat until light 1 to 2 minutes. Add the cocoa mixture and beat until smooth. In a small bowl stir together the sour cream and baking soda. Stir this mixture into the butter-sugar mixture. Add the flour and vanilla beat quickly just until evenly blended. With a spoon stir in the coconut.
Spoon the batter into the muffin cups dividing it evenly among them, they will be about three quarters full. Bake about 20 minutes until the tops spring back when lightly touched and toothpick inserted in the center comes out clean. Remove the tea cakes from the pan and cool slightly on a rack while you prepare the glaze.
Spread about 2 teaspoons of the chocolate glaze on each of the warm tea cakes and let cool thoroughly.
For the chocolate glaze: In a small saucepan combine the butter with 2 tablespoons water. Place over low heat, add the chocolate and stir until the chocolate melts and the mixture thickens slightly, remove from the heat.
In a small bowl combine the confectioner’s sugar and cinnamon, stir in the chocolate mixture and the vanilla to make a smooth glaze.
