Special equipment: an instant-read thermometer
For the maitre d'hotel butter: Place the butter in a bowl and stir until creamy with a rubber spatula. Add the lemon juice, lemon zest, parsley, shallots, 1/4 teaspoon salt and a pinch of pepper to the butter and mix well.
Transfer the butter to a sheet of plastic wrap and roll into a cylinder. Store in the refrigerator until it is firm. Slice the butter, still wrapped in plastic, into four 1/8-inch slices, removing the plastic around each portion. Leave the remaining butter wrapped for another use. The wrapped butter will keep in the refrigerator for one week.
For the pork chops: Heat 2 large pans over medium heat with 2 tablespoons vegetable oil in each pan. Season the pork chops on both sides with salt and pepper. Add 2 pork chops to each pan and cook over medium heat until the pork has a nice crust. Flip and repeat for the other side. The pork should be cooked until the internal temperature reads 155 degrees F. Remove from the pan and allow to rest. Add the onions to the pans with the pork drippings and cook over medium heat, stirring occasionally, until they are light brown and tender. Season with salt and pepper.
Heat a large nonstick pan over medium-low heat. Add the unsalted butter and whole bananas to the pan. Cook over medium-low heat, making sure not to burn the butter. Once the first side of the bananas become golden brown, flip them all and add the rosemary to the pan. Continue cooking until the other sides are golden brown and the bananas are tender. Season with salt and pepper.
Lay out 4 plates. Put one pork chop on each plate and cover with the sauteed onions and a pat of maitre d'hotel butter on the top. Serve the bananas on the side, garnishing with the rosemary and pan juices. Place half of a fresh lemon on each plate for squeezing over the pork chop, onions and bananas just before eating.