Preheat the oven to 400°F. Line a large baking sheet with parchment paper.
In the bowl of a stand mixer, sift flour into a large bowl and add sugar and cold butter. Mix the ingredients using the paddle attachment. If the dough doesn't come together, add a bit of cold water. Form a ball, wrap the dough in plastic wrap, and refrigerate for about 45 minutes.
Combine peach slices and orange zest in a medium bowl, toss to blend.
Roll the dough into 2 circles (each about 6 inches in diameter) directly on the lined baking sheet, dust with additional flour if necessary. Spread mascarpone in the center, leaving about 2 inches of free edge. Arrange the peach slices on top in concentric circles, overlapping slightly. Using parchment as aid, fold the crust border up over the peaches, pinching any cracks in the crust. Brush crust with canola oil.
Bake for about 35 minutes, until golden brown. Remove from the oven and let cool for 10 minutes before serving. Garnish with powdered sugar and mint leaves.
Notes
Tip: Pie tastes great topped with vanilla ice cream or Greek yogurt.