For the pheasant, heat a deep frying-pan with a splash of oil and add the red onion and pheasant cooking for 2-3 minutes, until beginning to colour.
Add the red wine, balsamic vinegar and stock cube with a knob of butter and bring to the boil.
Let this simmer for 15 minutes, or until cooked through and reduced.
Meanwhile, for the potatoes, preheat grill to highest setting.
Heat a saucepan of water until boiling and then par-boil the diced potato for 4-5 minutes.
Drain and stir through wholegrain mustard and rosemary with a fork.
Place a ring mould on a baking sheet and fill with the potato mixture, pressing down.
Top with crumbled Stilton cheese and place under the grill for 2-3 minutes, until bubbly.
Serve with the pheasant, drizzling over the red wine sauce.