Preheat the grill to medium.
Place two slices toasted bread onto a baking tray.
Mix the mustard with the grated cheese and season, to taste, with salt and freshly ground black pepper.
Spread the mixture over the toast. Place under the grill and grill until melted and bubbling.
Place the damson jam in a small saucepan and warm over a gentle heat.
To serve, slide the cheese on toast onto a serving plate and pour over the warm damson jam.