Preheat oven to 180°C.

Line a jelly roll pan or cookie sheet with parchment paper.

Melt the chocolate. Remove the chocolate from the heat source, add the sugar and oil, and whisk well. Add the eggs and mix. Add the vanilla sugar, cocoa, potato starch, ground almonds, and salt and mix well. Add the chocolate chips and mix to distribute them.

Divide the dough in half and shape into two loaves, each about 9 x 3 inches (23 x 7.5cm). Place both loaves on the lined jelly roll pan and bake for 30 minutes. Let the loaves cool for 10 minutes (do not turn off the oven). Cut each loaf crosswise into 3/4- to 1-inch-thick (2- to 2.5-cm) slices. Place the cookies, cut side up, on a parchment-covered cookie sheet (or the jelly roll pan again). Bake for another 14 minutes, or until the cookies are firm to the touch on the outside but still feel soft on the inside. Check them after 10 to 12 minutes so that you don’t over-bake the cookies.

Let cool for 5 minutes on the pan and then slide the parchment and cookies onto a cooling rack to cool completely.