Slice the ends off the orange then cut into thin slices using a sharp knife, about 3-6mm/1/8-1/4 inch thick.
Place the sugar and water in a pan and heat gently while stirring until the sugar has dissolved. Add the orange slices and bring up to a simmer, leave to simmer gently for about 40 minutes, until the liquid has reduced to a thick syrup and the oranges are soft and the peel has become slightly translucent. Turn the slices occasionally to unsure that they are evenly covered.
Preheat the oven to 180C/350F/gas mark 4. Grease three 15cm/8 inch tins (or two 20cm/8 inch ones) and line the bases with baking parchment.
In a large bowl, whisk together the almond milk, orange juice and zest, olive oil, sugar and vanilla and almond extracts until smooth. Whisk in the ground almonds.
Sift together the flour, baking powder, bicarbonate of soda and salt. Add to the wet ingredients and whisk gently until combined. Do not over-mix.
Divide the batter between the tins and bake for about 30 minutes until golden and firm to the touch and a skewer inserted into the centre comes out clean.
Leave the cakes to cool in the tins for 15 minutes then carefully turn them out onto a wire rack and leave to cool completely.
Melt the chocolate, either in a bain marie or in short bursts in the microwave. Set aside to cool a little.
Place the margarine and vegetable shortening in the bowl of your stand mixer (or you can use a hand mixer). Whisk until smooth. Add the cocoa powder and mix on a low speed until combined.
Add the sifted icing sugar and mix on a low speed until combined then turn the mixer up to a high speed and whisk for a good few minutes until light and fluffy. Scrape down the bowl every now and again.
Check that the melted chocolate is no longer hot to the touch then add it to the buttercream and whisk until smooth. Finally whisk in the extracts.
Trim the tops of the cakes if needed. Place one cake layer on a serving plate or cake stand and spread over a layer of the buttercream. Place another cake layer on top and repeat.
Place the last cake layer on upside-down (to give you a perfectly flat top). Spread a thin layer of buttercream over the top and sides of the cake. Place in the fridge for about 15 minutes to firm up.
Spread another layer of buttercream over the whole cake. Getting it as smooth as you can with a bench scraper or spatula. Return the cake to the fridge while you make the chocolate drip. (You want the cake to be cold when you add the drip).
Melt the chocolate, either in a bain marie or in short bursts in the microwave. Stir in the coconut oil until smooth and melted. Set aside to cool until it has thickened slightly and is no longer warm to the touch.
Use a spoon to drizzle the chocolate drip around the edge of the cold cake, using the back of the spoon to encourage it to drip over the edge. Spoon the rest into the middle so that the top of the cake is fully covered.
Return the cake to the fridge until the drip is set.
Place the leftover buttercream in a piping bag fitted with a star shaped nozzle. Pipe decorative dollops of buttercream on top of the cake as you like and top with a few candied orange slices.
The cake will keep in an airtight container at cool room temperature for a couple of days.