In a large bowl of a stand mixer (or using beaters or a wooden spoon), cream the butter with the sugar until light and fluffy, about three to four minutes, scraping down the sides of the bowl once or twice. In a separate bowl, mix the flour, oats, and salt together, then add to the butter mixture in three increments, beating as you add. If you’ve added all the oat mixture and the dough is still quite dry, add the water, one tablespoon at a time, until the dough comes together.
Between two large sheets of waxed paper or parchment paper, use a rolling pin to roll the dough out to about a six millimeter slab. Pull the top layer of paper off and cut the dough into circles about eight centimeter in diameter with a cookie cutter or the top of a glass. Transfer the oatcakes to an ungreased baking sheet—you should end up with about a dozen.
Bake the oatcakes for 15 to 20 minutes in the pre- heated oven, or until they begin browning very slightly around the edges. Remove from the oven, let cool for two to three minutes on the baking tray, then transfer to cooling racks.
To make these a little more decadent, melt the chopped dark chocolate over low heat in a saucepan or over medium heat in a double boiler. Once melted, remove from the heat and dip half of each oatcake in the chocolate, then lay on a cooling rack or piece of parchment to set. For the ultimate experience, sprinkle a little fleur de sel or flaky sea salt over the melted chocolate before it hardens. Whether sweet or savoury, these are always great with a dram of whisky.