The solar charge controllers are built with this idea.

So far I use the LM2588 for most things like this. You could build your own though. Study how the 2588 works.

If you build one an IGBT would work better than a MOSFET as the switching time is normally faster. Controlled by a Gate voltage like a MOSFET.

Things to consider no matter how you do it.

The diode will need to be heat-sinked so on in a TO-220 package works well.

The inductor is critical, you will spend more time sizing this than anything else. One thing about national.com is the web-bench. it will help size things.

The switching frequency is critical also.

This would be a good project for a PIC. Boost, control, and Display all in one.