Heat the oil in a medium saute pan over medium-high heat. Cook the bacon until slightly crisped, then remove to a plate lined with a paper towel. Add the bratwurst to the pan and cook until deep brown all over and an instant-read thermometer inserted in the center registers 165 degrees F, about 20 minutes total. Keep the bratwurst in the pan over low heat.
Heat a nonstick pan over medium heat. Slice the bun along the top and open like a book. Brush the inside with the butter and sprinkle with the Parmesan. Cook the bun in the pan face-down until golden brown, about 1 1/2 minutes. Set aside. Add the bacon to the same nonstick pan, top with the Cheddar and cover with a lid until melted, about 1 minute.
Microwave the peanut butter in a small heatproof bowl until warm enough to pour. Microwave the mango salsa in a small heatproof bowl until just warmed through.
To serve: Place the bratwurst inside the toasted bun, followed by half of the mango salsa and half of the peanut butter. Top with the melted cheddar and bacon and the remaining mango salsa and peanut butter.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.