Heat a large sauté pan over medium heat. Add the bacon, onion and garlic, and sauté until onions are translucent, about 10 minutes. Add the mushrooms and rosemary, and sauté another 4 minutes. Remove from heat and set aside.
Combine grits, milk, 1/2 teaspoon of the salt and 2 cups of water in a medium saucepan and bring to a simmer over low heat. Simmer for 15 minutes, stirring occasionally, then remove from heat, cover and let stand for another 10 minutes.
Whip the cream until soft peaks form. Fold the whipped cream, mushrooms, olive oil, Parmesan cheese, truffle oil, basil and black pepper into the grits.
To serve, spoon grits into a flat-bottomed tasting spoon. Top with julienned apple.