You are interchanging the words "paint" and "stain" but because I am familiar with the Minwax product you speak of, I understand you are not painting, but staining your cabinets. In order to stain wood, it must have NO finish on it or the stain will not permeate the wood.
If you are not happy with the color of the initial coat of stain, then you may have chosen a Minwax Polyshade that is too light in the first place. Because when the first coat of the stain/polyshade finish is applied, it seals the wood and therefore, another coat will not create a darker color.
It seems to me that you will have to sand off the finish and begin fresh with a darker shade of Minwax Polyshade. But, to perfectly honest, through my experience with stain, especially in a kitchen, you should use Minwax stain (not polyshade) and THEN put the separate Minwax Polyurethane (Satin, Gloss or Semi-Gloss finish of your choice) on, over the stain, in two to three thin coats. Yes, this is the more laborious route, but it will give you a better and longer lasting finish as the Minwax Stain and Minwax Polyurethane goes deeper into the wood and gives a better finish than using just the Polyshade.
Your local hardware store may sell tiny packets of stain for you to test on the inside of your cabinet (like the size of a ketchup packet). Well worth the money and effort to get the right color so you can proceed with confidence.