Preheat oven to 180°C bake and grease a 12-hole muffin tin or line with paper cases.
Cream Tararua Butter and Chelsea Soft Brown Sugar together until pale and fluffy. Beat in eggs one at a time, until combined.
Sift in Edmonds Self Raising Flour and cocoa powder and stir to combine. Fold in feijoas and chocolate chips.
Spoon mixture into prepared muffin tin and bake for 20-25 minutes, or until a skewer inserted into the middle of the cupcakes comes out clean. Leave in tin for 10 minutes, then transfer to a wire rack to cool completely.
While cupcakes cook, prepare mousse icing. Place feijoa flesh, Chelsea Caster Sugar and lemon juice in a small saucepan on medium heat. Simmer gently until you form a compote (about 10 minutes). Mix water and cornflour together and add to pan. Cook for 1-2 minutes, until thickened. Transfer mixture to the fridge to cool completely.
Whip Meadow Fresh Cream and Chelsea Icing Sugar together to firm peaks. Add cooled feijoa compote and fold in until just combined. Transfer mousse to a large piping bag (fitted with nozzle of your choice) and refrigerate for 30 minutes. Pipe mousse onto cooled cupcakes and serve.