Mmmm... beef and vegetable soup with lentils

A good casual recipe for when you feel like flinging some things in a pot and letting them simmer away while you read a good book on the couch. As long as you have the three ingredients in the title in reasonable proportions, it's hard to go wrong.

Beef and Vegetable Soup with Lentils
(based on Giada's recipe)

1 lb of stewing beef (don't bother using expensive cuts of meat - as with any wet cooking method, even economical cuts will come out very tender)
1 large onion, chopped
3 carrots, chopped
3 ribs of celery, chopped
a 32 oz. carton of beef stock (nobody makes their own, not even Ina)
water
2 tomatoes, chopped (or 1 can of chopped tomatoes, with juice)
1/2 cup dried lentils, rinsed, with stones and other debris picked out
salt and pepper

Optional seasonings: oregano; rosemary; bay; garlic; fresh parsley; Worcestershire sauce; soy sauce; tomato paste; a glug of red wine or Guinness (I wouldn't use all of them at the same time, but play with it until it tastes good to you.)

Brown the beef in some oil. Remove the beef to a dish and throw the onion, carrots and celery into the pot; sauté the vegetables a bit. Return the beef to the pot, along with any meat juices that have collected in the dish. Plonk in the tomatoes and pour in the beef stock. Top up with enough water to make it look like a soup (enough to cover the vegetables and beef by an inch or two, at least).

When it comes to a boil, taste before you start seasoning, as different brands of beef stock contain wildly different levels of salt. Start playing with the herbs and whatnot until you're satisfied. Err on the side of caution - the flavors do deepen as it cooks. Reduce to a simmer and let it be, for 30 min to 1 hour.

Some 20 min before you intend to eat, put in the lentils. If you stir through and can barely see the lentils, check the impulse to add a lot more. Don't worry - they expand.  The soup is done when the lentils are tender. I check the seasoning one last time before serving.

Variations: You can sub out the lentils for cannellini beans, pastina, etc.