Make the cookie butter pastry cream

• Whisk the egg yolks with the sugar and cornstarch in a bowl until smooth.
• Heat the milk in a saucepan until steaming, then pour it gradually over the yolk mixture while whisking.
• Return everything to the saucepan and cook over medium heat, whisking constantly, until thick.

Enrich with cookie butter

• Off the heat, stir the cookie butter into the hot cream until fully melted and glossy.
• Cover with plastic wrap touching the surface and let cool completely.

Fill the croissants

• Cut a small opening in the side of each croissant.
• Pipe the pastry cream generously into the croissants, then spread a little extra cookie butter inside.

Dip in white chocolate

• Melt the white chocolate gently until smooth.
• Dip the top of each filled croissant into the melted white chocolate.

Top and set

• Sprinkle the crushed Biscoff cookie crumbs over the white chocolate.
• Let the chocolate set before serving.