Day/hour before: Pop both oranges (skin on) in a pot with water, bring to the boil, then put the lid and reduce to a low simmer for one hour. Keep one cup of the cooking water aside.
Bake day: Preheat the oven to 160°C (320°F) on fan bake, and line the sides and base of a small 19 cm (8 inch) spring form cake tin with baking paper and then sunflower or another neutral oil. Make sure the baking paper comes up just over the tin (to hold your icing in place).
Blend the almonds in a food processor until a fine flour forms. Then add the remaining dry ingredients and blend again until combined. Turn out and sift into a large bowl - any bits that won't sift through, just pour on top of the other dry ingredients.
Next, blend all wet ingredients in your processor or blender until super smooth, including the two whole cooked oranges and the reserved orange cooking water. Fold the liquid mix into the dry ingredients, lifting gently as you pour to create air pockets, until only just combined.
Pour into your tin and bake for 60 minutes in the middle of your oven (not too high as these flours can brown easily). Test with a skewer at 55 minutes, and remove once it comes out relatively dry. If still wet at 60 minutes, bake for another 5-10 minutes.
Leave on the bench to cool, and after 5 minutes, pop open the springform outer of your tin to let the sides cool also.
Icing: Once cool, blend all icing ingredients in a high speed blender until super silky smooth like a cream, scraping down the sides and blending again as necessary. Close the springform tin again so the baking paper "party hat" is nice and tight around the cake once more. Then pour your icing on top of the cake - the baking paper and springform tin ring will hold it in place - place in the fridge overnight to set (or even in the freezer if you're in a rush).
Once firm, remove the tin outer and base, and baking paper, and using a sharp knife, run around the edge of the cake to remove any bits of icing that have bulged out (it tends to). Try to refrain from eating said icing off-scrapings. Fail (but enjoy it immensely). Decorate with edible flowers and serve with natural coconut yoghurt and fresh mandarin segments if you like. Enjoy!