Boekweitgrutten is an enduring historic Dutch countryside staple: roasted buckwheat groats slowly simmered in rich whole milk to a comforting porridge, served with a pool of melting farmhouse butter and dark Dutch kitchen treacle.
Rinse the buckwheat groats under cold running water in a fine sieve to remove any loose surface starch. In a heavy-based saucepan, combine the whole milk and a generous pinch of sea salt, heating over medium flame until tiny steam bubbles begin forming around the edge.
Stir the rinsed groats into the hot milk. Reduce the heat to the lowest setting, cover the pan with a lid, and allow the porridge to simmer very gently for 15 to 18 minutes. Stir every few minutes with a wooden spoon to prevent the buckwheat from catching at the bottom.
Once the groats have absorbed the milk and turned plump and velvety, turn off the heat. Keep the saucepan covered and allow the porridge to rest for 5 minutes off the hob, allowing the grains to finish swelling into a thick, spoonable consistency.
Ladle the steaming buckwheat porridge into deep warmed ceramic bowls. Press the back of a spoon into the centre of each portion to create a small hollow, drop in a generous knob of cold butter, and drizzle richly with dark Dutch stroop and brown basterdsuiker.