Make sure you whisk the oat flour right into the cold milk and coffee before you even think about turning on the stove. Starting cold is the real secret here because it keeps the flour from turning into stubborn clumps; just keep it moving as it warms up until it's thick enough to generously coat the back of your spoon.
Using grape molasses instead of standard sugar gives the coffee base a remarkably rich, caramel-like depth. Let the pudding chill in the fridge until it’s properly set, and wait to scatter those crushed roasted hazelnuts over the top right before serving so they stay wonderfully crunchy. If you ever find it sets a bit firmer than you'd like, just splash in a touch of extra milk to loosen things up.
