Start by greasing and lining two 8-inch cake tins (sandwich or deep ones will do). Preheat the oven to 160˚C for conventional ovens, 10-20˚ lower for fan forced ovens.
Beat the caster sugar and butter together for at least 5-7 minutes until very much paler, light and fluffy. Don't skimp on this bit, it helps with the rise and texture of the final bake.
Whisk the eggs, milk, vanilla and maple syrup together in a jug.
Pulse the pecans in a food processor until you have a fine crumb then add in the almonds, rice flour, buckwheat flour, baking powder and xantham gum. Blitz briefly to mix.
Gradually mix in the beaten egg mixture into the creamed butter, adding a spoonful of the flour mixture as you go to prevent curdling. Mix in remaining flour and divide between the two prepared cake tins.
Bake for 50-55 minutes until risen, browned and springing back to the touch when carefully pressed in the centre. A skewer should also come out clean when inserted into the centre.
Cool on a rack in the tins until you are able to turn them out. Gluten free cakes are more delicate so don't be tempted to flip it out after 5 minutes!
Beat the butter and icing sugar until light and fluffy then add in the vanilla and the cream cheese or cheesecake flavoured oils (I love LorAnn oils for this). Taste and adjust flavourings to your liking.
Scrape into a piping bag fitted with a 1-2cm plain round nozzle. Use a little less than half to fill the cake and the rest you need to pipe in a spiral from the centre out.
If using the melted chocolate, scrape into a small food bag and snip off the corner allowing about a 2mm opening. Pipe the chocolate along the ridge created between the swirls of the frosting. If using caramel instead, beat it to loosen and proceed as per the chocolate instructions.
Finish by sprinkling the edge with the chopped pecans, if desired.