Firstly, get the potatoes on the go for the accompanying mashed potato. If your kids will allow, leave the skins on as more nutrients are maintained. Likewise, the larger the pieces, the more nutrients maintained BUT the longer they will take to cook.
Next. Halve the onion and then slice so that you have semi circle onion rings. In a large frying pan, sauté them with the garlic if you are using until translucent.
Add the sausages either to the frying or if you are being more health conscious - under the grill - until they are nicely browned round the outside. This is necessary to stop them absorbing the liquid later and becoming soggy.
Add the can(s) of beans, tomatoes and tomato puree (if using) to the pan and hold at a fast simmer for as long as your tummy will allow! The longer it simmers, the thicker the sauce becomes. You can speed this process up by adding a little arrowroot or cornstarch. (remember to mix it up in a little cold water first then add to the hot liquid to prevent it from forming lumps.)