In a double boiler, melt the 250g of dark chocolate, the butter and coffee powder. Set aside to cool for 5 minutes
Meanwhile, in the bowl of a stand mixer, beat the sugar, eggs on medium speed for 5 minutes
Turn the mixer down to low speed and add the chocolate mixture and vanilla. Beat until just combined.
In another bowl, combine the flour, bicarb soda, salt and cream of tartar
Using a rubber spatula, fold the dry ingredients through the chocolate mixture, until just combined.
Place the dough into the fridge for an hour
Using an ice cream scoop, drop 2 scoops of cookie dough into each skillet and spread the mixture to reach the edges of the pan
Push the extra pieces of chocolate into the dough mixture
Bake at 180° celsius for 12-14 minutes
When cooked (and still soft in the middle) place skillet onto a heat proof plate or tray and serve with ice cream and caramel sauce