Preheat oven to 325°F and line a baking sheet with parchment paper.

Spread out the almonds and hazelnuts in an even layer. (Separate the almonds from the hazelnuts so it will be easier to remove the skin from the hazelnuts later.)

Roast the nuts for about 16 minutes, or until the hazelnuts are golden brown.

Remove from the oven, place the hazelnuts in a kitchen towel and rub with your hands to remove their skins. You only want to remove the skin from the hazelnuts, not from the almonds. Let cool.

Combine the sugar and water in a large saucepan. Heat on medium heat for about 5-6 minutes, the sugar will dissolve and the water will start to boil. Once there is no more water the sugar will start to caramelize. Do not stir. When the sugar has a light caramel color, add the nuts to the pan and stir quickly using a wood spatula to make sure all nuts are coated with caramel. The caramel will harden very quickly, this is okay. Pour the caramel and nuts onto a baking sheet or silpat. Let cool completely.

Once the caramel is hard, carefully break it into large pieces. Be very careful, the caramel is so hard that it can be sharp.

Place the praline pieces in the bowl of a food processor with the whole vanilla bean (not just the seeds) and pulse a few times until you get smaller pieces. Continue to process until it turns into a paste, about 5-7 minutes depending on your food processor. I like to keep a crispy texture with very small bits of caramelized nuts, if you prefer a smoother texture, process for another 10 minutes. The paste should be thick but pourable.

Place two 3-inch square cookie cutters on a baking sheet (or flat plate) lined with parchment paper.

Place the praline paste in a medium bowl, set aside.

Add the dark chocolate and cocoa butter to a double-boiler and heat on medium heat until fully melted. Once melted, pour the dark chocolate/cocoa butter into the praline paste bowl and whisk until well combined. Let sit at room temperature for about one hour, or until the paste has thicken.

When the paste is thick but still pourable, pour it into the cookie cutters. Place them in the fridge for about 2 hours, or until hard.

Remove from the fridge and unmold the praline paste. Let sit at room temperature for at least one hour. This step is important, if you try to dip the chocolates when they are still cold the coating will be too thick and there are great chances it will have white streaks.

Melt the dark chocolate and cocoa butter over a double boiler (I used a small bowl placed on top of a saucepan with water) . Cocoa butter is optional but helps thin out the chocolate, resulting in a thinner coating. Depending on the type of chocolate you use you might not need it (the higher the percentage of cocoa butter, the more fluid the chocolate will be).

Once melted, let the chocolate cool to 95°F. Stir in the micro planned cocoa butter and stir well to make sure it is well incorporated. This step will temper the chocolate, resulting in a crispy and glossy coating, without any white streaks.

Spread out a thin layer of melted chocolate on top of the two praline squares. Wait about 1 minute, flip them and spread a thin layer of chocolate on the other face.

Using a sharp knife, cut the two squares into 32 smaller squares. Using a dipping fork, dip each square, one at a time, into the melted chocolate. Tap the fork on the side of the bowl to remove excess chocolate and place the chocolate covered praline on a silpat or parchement paper. Sprinkle with some crushed hazelnuts or almonds. Repeat with the other pralines.

Let the chocolate harden at room temperature, do not place them in the fridge or you might get white streaks.

Chocolates will keep in a box for a least 1 month at room temperature.