Umm, maybe? If you're planning on manually grinding the almonds you certainly will. 
Right, recipe is from a Richard Bertinet book, as follows:
Creme d'amande
(Makes around 500g)
Beat 125g unsalted butter (at room temperature) and 125g caster sugar by hand, or mix in a food processor with a paddle, until pale and fluffy.
Add 125g ground almonds and mix again.
Add 25g plain flour and continue to mix.
Finally add 2 eggs (large), one at a time
Mix well between each addition, until the cream is light in consistency.
Use immediately, or store in and airtight container in the fridge for up to a week. [I have also frozen this, with no ill effects]
Almond croissant
Use 2-3 day old croissants - fresh will collapse under the filling and topping.
Cut croissants in half lengthways.
Brush the cut sides with sugar syrup.
Spread the inside of one half with creme d'amande (a couple of tablespoons should do).
Sandwich the 2 halves back together.
Holding the reassembled croissant in one hand, use a palette knife to spread another couple of tablespoons of creme over the top
Sprinkle with flaked almonds
Bake in a pre-heated oven at 190C for 8-10 mins, until the almonds on top have turned golden.
Apparently if you want to be particularly decadent 2-3 day old pain au chocolat may be used instead...