12 jumbo pasta shells
3 tbsp butter
2 ounces prosciutto, fat trimmed, chopped
2 large shallots, chopped
8 ounces cremini or button mushrooms, chopped (about 3 cups)
1/2 cup Ricotta cheese
2 tbsp chopped fresh basil or 1 tbsp dried, crumbled
2 tbsp chopped fresh parsley
1 15-ounce container prepared marinara sauce (about 2 cups)
1/2 cup freshly grated Parmesan cheese
1. Preheat oven to 350 F. Cook pasta in large pot of boiling salted water until just tender but still firm to bite, stirring occasionally to prevent sticking. Drain.
2. Meanwhile, melt butter in heavy large skillet over medium-high heat. Add chopped prosciutto and shallots and cook until shallots are translucent, stirring frequently, about 4 minutes. Add chopped mushrooms and cook until tender and juices evaporate, about 8 minutes. Remove from heat. Stir in ricotta, basil and parsley. Season to taste with salt and pepper.
3. Pour marinara sauce into bottom of 8x8-inch baking dish. Spoon 1 rounded tablespoon mushroom mixture into each pasta shell. Place in prepared dish. Top with grated Parmesan. (Can be prepared 1 day ahead. Cover and refrigerate.) Bake until heated through, about 20 minutes. Transfer shells to plates. Spoon sauce over and serve.