Add the salt and yeast to the warm water and stir to dissolve. Let rest 5-10 minutes to allow the yeast to bloom.
Place the flour in a large bowl. pour in the yeast and water mixture along with the olive oil. Using a spatula stir to bring together into a dough.Transfer to dough to a lightly oiled surface. lightly oil your hands and knead the dough until soft and elastic, about 5 minutes. If dough starts to stick, add a little more oil.
Place the dough in a bowl that has been lightly oiled and cover with a slightly damp tea towel. Place in a warm spot and allow to rise until doubled in size, about 1-1½ hours.Note: you can let the dough rise and then sit a bit longer until you are ready to pull together your pizza.
Prepare the Topping
Preheat the oven to 475°F
Peel the potatoes and slice thinly with a mandolin if you have one, or by hand.Place the sliced potatoes in a bowl and toss with olive oil and salt and pepper. Transfer to a parchment lined baking sheet. Spread the potatoes to lay flat, with no overlapping.Place in the oven to roast until golden brown, about 10-15 minutes. Set aside.
Start the onions while the potatoes are roasting.Heat 2 tablespoons of olive oil in a non-stick frying pan over med-high heat.Add the thinly sliced onions and cook until well browned, about 10-15 minutes.Once the onions are browned add the minced garlic and anchovy fillets and cook for another 2-3 minutes, using the back of a spoon or spatula to mash the anchovy fillets. The anchovy fillets will melt completely in with the oil and onions.Set aside while you prepare the mascarpone.
In a small bowl, combine the mascarpone, lemon zest and thyme (or sage) and a good grind of pepper.
Assemble the Pizza
Oil a pizza stone or baking sheet.Lightly flour your work surface and roll out the dough to a 12 inch diameter circle, or a 12 x 10 inch rectangle. carefully transfer to the pizza stone or baking sheet.
Spread the mascarpone mixture evenly across the dough, leaving ⅛ to ¼ inch edge. Sprinkle with more freshly ground pepper if desired.
Scatter the caramelized onion mixture evenly on top of the mascarpone mixture. then layer on the potatoes.
Layer on the potatoes and scatter the pitted olives over the top, drizzle with olive oil. Bake for 15-20 minutes, until the edges and bottom are golden brown.Note: if the top is becoming too browned before the bottom is cooked, cover with foil and let bake until the bottom is done.