Coarsely chop the chocolate. Place 6 ounces of the chocolate together with the butter pieces in a heatproof, microwave safe bowl or the top of a double boiler. If using a microwave, microwave for 3-5 segments of 30 seconds on high, stirring in between to help melt. If using a double boiler, place the double boiler (or any heatproof bowl) over gently simmering water, taking care that the water doesn't touch the bottom of the pan. Stirring until the chocolate and butter are just melted, then remove the bowl from the heat.

Immediately whisk in the granulated sugar into the melted chocolate. The mixture will turn grainy.

One at a time, add in the eggs, whisking for one minute after each addition. The batter should become quite smooth, shiny, and noticeably thicker. Whisk in the vanilla and salt.

Using a silicone spatula, fold in the flour until it just disappears. Fold in the reserved 2 ounces of chopped chocolate. The dough will be very sticky.

Cover the batter with plastic wrap or in an airtight container and refrigerate for at least 3 hours.

Preheat the oven to 350 F. Line a baking sheet with parchment paper or a silicone liner. Place about 1/3-1/2 cup of confectioner's sugar in a small bowl. Using a small cookie scoop, scoop out round portions of the dough, and roll each ball in the confectioner's sugar to create the snowy top. Once the ball is generously coated in confectioner's sugar, place it on the baking sheet. Repeat for the remaining dough, spacing cookie balls 2 inches apart.

Bake only one baking sheet of these cookies at a time, for a total of 12 minutes, rotating after 6 minutes. The cookies should spread and crack, with set sides, but will still appear fairly underbaked in the middle. This is how they should look.

Set the cookies on a metal cooling rack to cool at least 2-5 minutes, then serve warm or at room temperature.

Unbaked dough can be stored in the refrigerator for up to 4 days and in the freezer for 1-2 months. Once baked, these cookies will keep 3-4 days but will gradually lose their softness.