1. Preheat the oven to 500°. Preheat a pizza stone or generously oil a large baking sheet. Melt the butter in a large skillet. Add the leeks and cook over moderate heat until just softened but still bright green, about 5 minutes. Transfer to a bowl and let cool. Stir in the chicken, half of the Fontina and the olives and season with salt and pepper.
2. On a lightly floured surface, roll or stretch the dough to a rough 14-inch round. Transfer the dough to a floured pizza peel or rimless cookie sheet, or to the oiled baking sheet. Spread the chicken and leek mixture on the pizza, leaving a 1-inch border of dough. Brush the border with the olive oil. Sprinkle the remaining Fontina over the top and season with pepper.
3. Slide the pizza onto the hot stone, if using, and bake for about 10 minutes on the stone or 16 minutes on the baking sheet, until the crust is golden and the cheese is bubbling. Transfer the pizza to a rack and let cool slightly before serving.
Wine Recommendation: The pungent leeks point to a crisp California Sauvignon Blanc. Try the 1997 Quivira or the 1997 Mill Creek.