Remove the pizza dough from the refrigerator 1 hour before you ready to start.
In a large saute pan over medium low heat add 2 tablespoons of olive oil. Add onions and slowly caramelize until brown and creamy about 20 minutes. Set aside to cool.
Preheat oven to 500 degrees F.
Heat the grill over medium-high heat and wipe down with oiled paper towels to create a non-stick surface. On a floured surface, roll out each of the pizza dough into an elongated shape, about 12 by 8-inches and about a 1/2-inch thick. Brush with olive oil and grill on both sides until warmed through and grill marked, about 4 minutes per side. Transfer to a baking sheet.
In a medium bowl, mix together the mascarpone and blue cheese. Smear the cheese mixture over each of the grill pizza crusts. Place in oven for 2 to 3 minutes until the cheese melts. Remove from oven and transfer to cutting board or platter.
Top with caramelized onions, toasted walnuts and fresh grapes. Season with a few turns of freshly ground black pepper, drizzle with some more extra-virgin olive oil and top with fresh parsley.