Make gravy. sauté sliced onions in butter. add rest of ingredients and stir well. Bring to simmer and simmer until desired thickness. Should still be somewhat lose but full of flavor.
grill bangers in a buttered pan
cook potatoes in oven, steamer, pressure cooker or boiling water until tender
mash potatoes with butter, salt and pepper
when banger sausages are done drop peas in pan to warm them up.
serve potatoes topped with bangers topped with gravy and peas on the side.