Step 1: In the top of a double boiler, combine 1/2 cup softened butter, cocoa powder, and sugar. Stir occasionally until melted and smooth. Beat in egg and stir until thick, 2 to 3 minutes.
Step 2: Remove from the heat and mix in graham cracker crumbs, coconut, and almonds. Press into the bottom of an ungreased 8x8-inch pan.
Step 3: For the middle layer, beat remaining 1/2 cup softened butter, heavy cream, and custard powder until light and fluffy. Mix in confectioners sugar until smooth. Spread over the bottom layer in the pan. Chill to set.
Step 4: While the second layer is chilling, melt semisweet chocolate and 2 teaspoons butter together in the microwave or over low heat.
Step 5: Spread melted chocolate mixture over chilled bars. Let the chocolate set before cutting into squares.