Everything needs a catchy name, so I call it Debugger Driven Development.
I write the first few lines of a function, however much I feel sure about, then add a dummy statement at the end and set a breakpoint there. When the code stops at the breakpoint, I can see exactly what my code did and what data I now have on hand.
I use that new knowledge to write the next few lines, again until I get to something I'm unsure of or where I'd just like to get a better view of the data. Set a breakpoint there and view that new data.
Repeat as needed until the function is done.
At my work we have many internal APIs that are "documented" but the documentation is fairly lacking. With the debugger, I can see not only what the API claims to do, but what it really does with my actual input.
I am bummed that so many developers today eschew debuggers. I even read an article recently along the lines of "These famous programmers don't use debuggers, and you shouldn't either". Why would anyone want to talk people out of using such a useful tool? It makes no sense to me.