Pre heat your oven to 180°C (356°F). Grease and line your loaf tin.
Add the flour, brown sugar, baking soda, all spice and cinnamon to a bowl and mix well.
Slice the feijoas in half length ways and scoop out the flesh. Put into a bowl and lightly mash with a fork.
Put the butter into a microwave proof bowl and melt in the microwave.
Add the vanilla essence and eggs to the feijoas and mix well. Add the butter and milk and mix well.
Add the wet ingredients to the dry ingredients and mix until just combined. The should be no unmixed flour, but don't over mix the batter or your will have a dense cake.
Tip the cake batter into the line loaf tin. Bake for45 minutes or until golden brown.
Remove from the oven. Allow to cool for a few mins and serve warm or cool with butter. Delicious!