Will I be able to recover unpaid overtime from my employer?

If your employer is paying you an hourly wage, then you are entitled to be paid overtime at the rate of time and a half.  Regardless of whether he pays you the under the table or by check, you are still entitled to an additional rate for the unpaid part of the overtime.  Your employer is most likely subject to the FLSA depending on whether he makes or uses products that are sold or purchased outside of your state.  But there are also state overtime wage laws that would apply even if he is not under the FLSA.  See an attorney about this