To cook the feijoas, place the feijoas, lemon juice and sugar in a heavy-based saucepan.
Place over medium heat and cook, stirring from time to time until the feijoas are soft and the mixture is jam-like. Remove from the heat and set aside to cool and thicken further. (This can be done a day ahead if wished).
Heat the oven to 160C. Grease and line a slice tin (20cm x 30cm) with baking paper.
Make the base, place the rolled oats, coconut and almonds in a food processor and process 2-3 times until combined.
Add the dates, vanilla extract and butter and process until the mixture begins to form large clumps. Remove and place in the prepared tin, pressing down until the mixture is smooth and even. The back of a spoon is helpful here.
Place in the oven and cook for 20 minutes. Remove from the oven and set aside to cool.
To finish, spread the feijoa mixture over the base and top with the muesli, pressing it gently into the feijoa mixture. Drizzle over a little raw honey if using. Place in the fridge to firm up before slicing.