To make the polenta, heat milk and heavy cream in a large pot and bring to a boil then reduce heat to a simmer.
Slowly add the polenta stirring constantly for 6 to 7 minutes, or until the liquid has been absorbed.
Remove from heat, stir in mascarpone and parmesan, and season with salt and pepper to taste.
To make the spring peas and pearl onions, cook onions in large pot of lightly salted water for 2 minutes.
Drain and cool.
Preheat oven to 400 degrees F.
Transfer onions to shallow baking pan.
Drizzle with 1 tablespoon olive oil, season with salt and pepper, and toss to coat.
Bake until tender and golden, shaking pan occasionally to turn onions and brown, about 10 minutes.
In a large skillet, heat 2 tablespoons olive oil and 2 tablespoons butter over low to medium heat.
Add garlic and quickly sauté for 1 minute.
Add the onions and peas; simmer until onions and peas are crisp-tender, about 4 minutes.
Add 4 butter, stir until melted.
Season with salt and butter.
For the lemon gremolata, gently mix together the parsley, pine nuts and lemon zest in a small bowl; season with salt and pepper.
To make the lamb osso buco, preheat oven to 325 degrees F.
In a nonstick pan, cook pancetta over medium heat just until fat is rendered.
Remove pancetta from pan and set aside.
In a large sauce pot, heat ¼ cup olive oil over medium heat.
Reduce heat to low, add onions, carrots, fennel and garlic.
Cook very slowly until very soft.
Transfer vegetables to a roasting pan large enough to hold the lamb shanks in a single layer.
Season shanks with salt and pepper.
Heat ¼ cup olive oil in a large pan until very hot.
Sear shanks until browned.
Transfer shanks and cooked vegetables to a roasting pan.
Add pancetta, red wine, veal stock, thyme, lemon and orange zest.
Cover roasting pan with foil and roast for 2 to 2½ hours until the meat is tender.
Remove osso buco and use the same liquid for the sauce, skimming the fat off of the top.
Serve osso buco over creamy polenta with spring peas and pearl onions.
To finish, garnish with gremolata.