Step 1 First, cook the new potatoes, allow them to cool a little before peeling them.
Step 2 Separate the leaf from the stalks of the chard, cut the stalk into half centimetre chunks and shred the leaves.
Step 3 Cook the stalks in the stock until tender adding the leaves to cook for a minute at the end.
Step 4 Make a roux by cooking the flour and butter together gently in a sauce pan until you have a sandy texture, then begin adding in the warm stock from the chard, a little at a time, stirring well to avoid making it lumpy.
Step 5 Incorporate all the stock before adding the milk & mustard to make your sauce. Taste and season with salt and fresh black pepper to your liking.
Step 6 Gently stir in the sliced new potatoes, ham, cooked chard & half of the grated cheese.
Step 7 Pour the mixture into a suitable sized oven proof dish, top with the remainder of the cheese and the breadcrumbs and cook in a moderate oven for half an hour until golden on top.