For the dressing, mix the mustard, maple syrup and cider vinegar together in a bowl. Gradually whisk in the oil to make a thick vinaigrette. Season to taste with salt and pepper and set aside.
Peel, quarter and core the apples, then cut into eighths. Melt the butter in a large non-stick frying pan, add the apples, sugar and some salt and pepper, then toss gently to coat. Cook over a medium heat for 7-8 minutes or so, turning halfway through, until just soft and nicely caramelised.
Meanwhile heat another large non-stick frying pan over a medium heat. Add the bacon lardons and cook gently for 1-2 minutes until they've released some of their fat. Increase the heat to high and stir-fry until they're crisp and golden. Lift onto a plate with a slotted spoon and keep warm. Turn off the heat under the apples when they're done; keep these warm too.
Pour away most of the fat from the bacon frying pan and return it to a high heat. As soon as it starts to smoke, add the scallops and sear for 2 minutes, seasoning with a little salt and pepper as they cook. Flip them over, season lightly, then add the black pudding to the pan. Cook the scallops for another 2 minutes, and the black pudding for 1 minute on each side. Immediately remove the scallops and black pudding to a warmed plate.
Arrange the winter salad leaves over a serving plate (or 4 individual plates), then arrange the scallops, black pudding slices, butter-fried apples and crispy bacon lardons in among the leaves. Whisk the dressing again, then drizzle over the salad. Serve straightaway.