I'm looking for the BEST brisket recipe in the world?

A friend and I are preparing a belated Rosh Hashanah dinner early next week.

I had the best brisket last year but can’t get the recipe! I know it had potatoes, carrots, and onions… and was in the most savory, delicious sauce.

My mom swears that her brisket, marinated in mustard and ketchup, amongst other ingredients, is really great… but I’m not so sure.

What do you recommend? Any tips on cooking it (I’m still pretty new to this!)?