Potato, Parmesan, and Anchovy Focaccia

INGREDIENTS

• 1/4 cup freshly grated Parmesan
• 1 tablespoon coarse salt, or to taste
• 1 1/2 pounds small red potatoes, scrubbed
• 2 garlic cloves, sliced thin
• 2 teaspoons table salt
• 1/2 teaspoon sugar
• 1 cup lukewarm water
• 1/4 teaspoon anchovy paste, or to taste
• 4 to 4 1/2 cups all-purpose flour
• 1 tablespoon fresh rosemary leaves, chopped fine, or 1 teaspoon  crumbled dried
• 2 cups mashed cooked peeled russet (baking) potatoes (about 1 1/4 pounds)
• a 1/4-ounce package (2 1/2 teaspoons) active dry yeast
• 6 tablespoons olive oil