This is usually what I do with leftover roast beef since we can never seem to finish eating a whole one. Amounts are just a guesstiment since it depends on how much you have leftover. Making it this way, it seems like your not having the same dish 2 nights in a row.
This is one of my mom's recipes. I was sick with a summer cold and this really hit the spot. Hardly any effort. It's soup the first night and it's not so much like a soup the next day. The noodles soak up the liquid but it's still REALLY good!