Preheat oven to 475°F with a pizza stone or inverted sheet pan inside.
Thinly slice 1 Yukon Gold potato (use a mandoline for evenness). Toss them in a little olive oil, salt, and pepper.
1 Yukon Gold potato
Sauté the sliced 1 medium leek in 1 tbsp olive oil over medium heat until soft and slightly caramelized. Set aside.
1 medium leek, 1 tbsp olive oil
In a small bowl, mix 1/2 cup mascarpone cheese and 2 tbsp Boursin cheese until smooth and spreadable. Add a pinch of salt and pepper.
1/2 cup mascarpone cheese, 2 tbsp Boursin cheese
Lay 2 slices prosciutto on a parchment-lined sheet pan and bake for 8–10 minutes until crisp. Let cool, then break into shards.
2 slices prosciutto
Stretch or roll out the 1 ball pizza dough to about 12 inches on a lightly floured surface.
1 ball pizza dough
Spread the mascarpone-Boursin mixture evenly over the dough, leaving a small border.
Layer the potato slices in an overlapping circular pattern. Scatter over the sautéed leeks. Sprinkle the shredded 1/2 cup fontina cheese and 2 tsp fresh thyme leaves evenly over the top Drizzle lightly with olive oil and sprinkle with Salt & pepper.
1/2 cup fontina cheese, 2 tsp fresh thyme leaves
Transfer pizza to the hot stone/sheet and bake for 8–10 minutes until the crust is golden and crisp, and the potatoes are tender.
Remove from the oven, top with crispy prosciutto shards, fresh thyme leaves, and a pinch of flaky salt.
Slice and serve immediately.