For a simple stew like this, I think mutton has the best flavour. Maple peas or carlings are not that common, though you tend to find them in the north of England. If you can't find any, you can substitute chickpeas instead.
1kg neck fillet of mutton, cut into rough 2cm pieces
Plain flour for dusting
2 large onions, peeled and finely chopped
Vegetable oil for frying
A small sprig of rosemary
Salt and freshly ground black pepper
1.5 litres chicken or lamb stock (can be made with good-quality stock cubes)
80g maple peas, soaked in cold water overnight
1tsp bicarbonate of soda
2tbsp chopped parsley
Season the pieces of mutton and dust generously with about a tablespoon or so of flour. Heat the vegetable oil in a heavy-bottomed saucepan and fry the pieces of mutton and onions, without colouring them too much, for 3-4 minutes.
Add the rosemary and stock, bring to the boil and simmer gently for about 1-2 hours until the mutton is soft and tender. This may take a little longer, or it may be quicker, as it's difficult to put a cooking time on braising cuts. You may need to add a little stock or water during cooking if the stew is getting dry.
While the mutton is cooking, place the maple peas in a pan, cover with water, add a couple of teaspoons of salt and the bicarbonate of soda, bring to the boil and simmer for 30-40 minutes or until tender, then drain. Add to the mutton and continue to simmer for about 15 minutes; then add the parsley and serve.