In a large skillet over medium heat, cook the onions with a little bit of salt and pepper, until they are very soft and caramelized, about 20-25 minutes.
Add a couple of tablespoons of water from time to time to help deglaze the pan and soften the onion. Always wait until all the water has evaporated before adding more.In a small saucepan, bring the balsamic vinegar to a boil. Lower heat and simmer until you are left with only about a tablespoon of vinegar. This should take about 15-20 minutes.Preheat your grill to medium high heat
Roll or stretch dough into 10-12 inch disc.
Brush one side lightly with olive oil. Make sure you have all your topping ready at this point.Throw your pizza dough on the hot grill and lower the heat to medium.
Lay your peach slices next to your pizza dough. Close the lid and cook for about 2-3 minutes.Flip your pizza dough and top it with caramelized onions and mozzarella cheese. Flip your peach slices, close the lid and continue cooking for another 2-3 minutes, until cheese starts to melt.
Remove pizza from the grill and top with peach slices, blue cheese crumbles, toasted walnuts, fresh sage and arugula.
Drizzle balsamic reduction, cut into wedges and enjoy!
