Roast the almonds and hazelnuts at 150°C / 302° F for 10 to 15 minutes.
Rub the hazelnuts between your hands to remove as much skin as possible. It's not a problem if some remains. You can also choose not to blanch them if you want a darker praline paste with a stronger flavor.
Place the sugar and butter in a large frying pan over medium heat.
Let the sugar caramelize, stirring occasionally. Once it has a nice amber color, neither too light nor too dark, you can stop cooking. It should be slightly darker than in the photos above, without burning, for a well-balanced flavor.
Pour in the almonds and hazelnuts and mix well.
Pour onto a marble slab and leave to cool. Don't touch it with your hands, as it's very hot.
Place on a large sheet of baking parchment and, using a rolling pin covered with cling film, lightly crush.
This step makes the robot's work easier. If you have a mortar, now's the time to use it.
Blend until you obtain a smooth, liquid, and creamy paste.
Remember to take breaks to let your food processor cool down from time to time; take advantage of this time to do something else while waiting.
Once ready, keep your praline paste for your next creations: entremets, cakes, brioches... But be careful, don't leave it within reach of children (or food lovers), they might finish it with a spoon!