Heat peas, half the onions and the bay leaf in the stock. Bring to a boil and down to simmer 25 minutes. Season lightly with salt and pepper towards the last few minutes.
In a separate, largish pan, fry the mustard seeds in the melted butter for 30 seconds or until the kernels begin to pop. Add reserved onion, and measures of garlic, ginger and bell pepper.
Saute for 5 minutes or until vegetables have softened before adding remainig spices. Add the split peas and tomatos and an additional water that may be needed before simering an aditional 10 minutes.
Check for seasoning, salt and pepper to taste and serve with optional garnish.