Preheat oven to 350°F. Make orange syrup by dissolving the sugar on medium heat in 100% natural orange juice (I squeezed out a big naval orange to extract the juice). You could cut down on the sugar a bit if the orange juice is very sweet. Let it come to a boil, remove and allow it to cool.2. Process the almonds with sugar in a food processor. When finely ground add the softened butter and pulse until well combined.3. Drop an egg into it, add vanilla, almond essence and process more until the mixture is smooth and creamy.4. If your croissants are not 3 days old then follow this. Cut open the croissants horizontally like a sandwich with out splitting them into two. Place them in a toaster oven preheated at 350°F for 5 minutes then switch off the oven and leave them there till they dry up a bit and are no longer soft. Allow them to cool down.5. Brush the croissants with the orange syrup well and arrange them on paper towels.6. With a piping bag fill each croissant with around 2 tbs of almond butter cream inside, close and pipe around one tbs over the top. Spread it lightly only lengthwise as it will spread across its width when it bakes on its own. Then over turn the cream side of the croissant into the bowl with the almond slices in it so that they get stuck on the cream. Repeat for all the croissants.7. Place them on a baking sheet lined with Silpat or parchment paper and bake them in the oven for 15 - 20 minutes. Mine were done in 20 minutes. Remove and allow them to cool for at least 1/2 an hour.8. Dust them with icing sugar and/or cocoa powder and enjoy them with a cup of coffee or hot chocolate. You could also make different variations such as with hazelnut cream, pistachio cream, nutella, chocolate butter cream and enjoy.