First, get a large pot of water on to boil for the pasta. While it comes to a boil, get out a big skillet with deep sides and heat the olive oil in it over medium high heat. Add the diced chicken and cook it through completely. While it cooks add the garlic, thyme and lemon juice to make everything fragrant. Season it with a pinch of salt and pepper too. Once the chicken is cooked, remove it to a plate and start on the sauce. Turn the heat to medium low. Add 1 1/2 cups of the heavy cream, half and half, butter and another pinch of salt to the pan and let it all meld together while you stir it. 

It should take about 3 minutes for the butter to melt and the sauce base to come together. While it cooks, boil the fresh fettuccine. Salt the pasta water generously and let the fettuccine cook in it for just a minute or two, until tender. Fresh pasta cooks really quickly. Drain it and set it aside for a minute. The sauce should be done by this point. Turn the heat to low and stir in the parmesan and remaining 1/2 cup of heavy cream until it all melds together. Add the chicken and cooked fettuccine in next and toss it all together thoroughly for a minute on the low heat. This will let the fettuccine and chicken absorb the sauce. Serve immediately and enjoy!!