In a medium bowl, beat together the cream cheese, peanut butter and sugar until smooth. Pour in the heavy cream and mix to combine.
Cut the chocolate cake into 3 pieces horizontally. Using a cutter the same size as your serving glasses, cut rounds of cake.
To assemble, layer the chocolate cake and peanut mousse with some chocolate sauce and crushed peanut brittle between each layer. Finish with some softly whipped heavy cream, more crushed peanut brittle, chocolate sauce and some chocolate shavings.