Bring a large pot of heavily salted water to a rolling boil. Add the tagliatelle and cook according to package directions until al dente. Before draining, reserve about 1 cup of the starchy pasta water. Drain the pasta and set aside.

While the pasta is cooking, melt the unsalted butter in a large skillet or non-stick pan over medium heat. Add the minced garlic and sauté for 1-2 minutes until fragrant, being careful not to burn it.

Pour in the heavy cream and bring it to a gentle simmer, stirring occasionally. If using mascarpone cheese, whisk it into the cream until smooth and fully incorporated.

Reduce the heat to low. Stir in the freshly grated Parmesan cheese until it melts into the sauce and thickens slightly. Remove the pan from the heat and stir in the white truffle oil and black truffle paste (if using). Season with freshly ground black pepper and a pinch of salt to taste. Remember, Parmesan cheese and pasta water are already salty.

Add the drained pasta directly to the skillet with the truffle sauce. Toss gently with tongs to ensure every strand is coated. If the sauce seems too thick, add a tablespoon or two of the reserved pasta water at a time until it reaches your desired consistency.

Serve the Truffle Pasta immediately in warm bowls. Garnish with a sprinkle of chopped fresh parsley and extra freshly grated Parmesan cheese, if desired.