In a bowl, combine the flour, baking soda, salt, and 340 gr. chocolate chips, and set aside.
In another bowl, combine the butter, sugar, and vanilla and mix to a creamy consistency.
Add the eggs one by one.
Then slowly add the flour, baking soda, salt and chocolate chip mixture.
Cover with a plastic wrap and refrigerate for an hour or overnight.
Preheat the oven to 350 degrees.
Using an ice cream scoop or spoon measure 38 balls of dough. Place each ball on a baking tray lined with parchment paper leaving about 2 inches between the biscuits.
Bake for 7 minutes. Let the biscuits cool down on the tray before removing them.
Heat the remaining 200 gr. chocolate chips over a double boiler (you can do the same using a glass bowl and heating it in a microwave for about 2 minutes). Mix with a whisk until the chocolate has melted.
Pipe out the melted chocolate onto a biscuit and top with another to create the “sandwich.” Let the chocolate cool.