Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper.
Place the prosciutto slices in a single layer on the prepared baking sheet. Bake until the prosciutto is starting to brown and becoming crispy, about 10 minutes.
Let cool slightly, then break into small pieces. Set aside.
In a medium bowl, stir together yeast, warm water and agave nectar. Let rest until yeast blooms and bubbles form on top, about 10 minutes.
Stir in flour, 3 tablespoons olive oil and 1 teaspoon kosher salt. Turn the dough onto a well-floured surface and knead until the dough is smooth, 5 to 10 minutes.
Add the crumbled prosciutto, prunes and 1 tablespoon rosemary. Knead to incorporate.
Place dough in a bowl coated with cooking spray, cover with a clean kitchen towel and let rest in a warm place until dough doubles in size, about 1 hour.
Preheat the oven to 450 degrees F.
Remove dough from the bowl and press it into a lightly oiled 9- by13-inch bakingsheet until it touches the edges. Using your finger, poke holes all over the dough.
Let rest until the dough becomes puffy, about 20 minutes.
Top the dough with the remaining 1 teaspoon kosher salt and 1 tablespoon rosemary. Drizzle with 2 tablespoons olive oil.
Bake until the focaccia is golden brown, 12 to 15 minutes. Allow to cool on thebaking sheet, then cut into 12 pieces. Serve.