Source: My mom
adapted by http://theresalwaysthyme.blogspot.com/
Everything is approximate. I got this by watching and writing it down as my mom cooked. You have to keep tasting to see if it needs more ketchup or pepper or whatever. Originally came from my Aunt Ruthie, who owned a luncheonette in NY.
brisket - flat (or first) cut 1/2 cup water
1 bottle Heinz ketchup (I think I used the 24 ounce size, more or less, you have to taste the sauce to see if it needs more)
8 carrots -- sliced in 1/4" thick coins
4 stalks celery -- sliced 1/4" thick
potatoes -- cut in chunks
2 large onions -- diced or sliced
salt and pepper -- to taste
First put the water (about 1/2 cup or so) in the pot, add the onions, salt and pepper. Then add some (about a 1/4 to 1/2 bottle) ketchup, and bring to a boil. Put in the brisket when it begins to boil. Lower heat to medium-low. Cook the brisket for a while, add a little more ketchup. Let it cook for an hour or so, covered, then take it out and slice it against the grain. Put the meat back in the pot and then add the potatoes, celery, and carrots. Cook on medium, covered, at just boiling, for another hour or more until the meat is tender and the vegetables soft. Remember to stir it really well a few times, otherwise what's on top of the pot won't be as tender what's on the bottom. Ask me how I know. My kids hate undercooked potatoes :) Keep tasting to see if it needs more ketchup, salt or pepper. Add ketchup as needed. Everything is approximate; you'll probably use a whole bottle of ketchup. Tastes even better the next day. Freezes well, except for the potatoes. If I make it ahead, I just boil up potatoes separately for when I'm serving and throw them in the pot!