Preheat oven to 400 degrees. Place a large pot of water over high heat and cover. Place a large saute pan with 2 tbsp oil or bacon grease over medium heat. Once oil is hot, add mushrooms to the pan and saute for 7-10 minutes or until fully cooked and slightly caramelized. Toss or stir occasionally. Season with a pinch of Kosher Salt and Black Pepper then deglaze the pan with the Sherry Vinegar. Allow all of the vinegar to cook out, then remove the mushrooms from the pan and set aside.
Now time for the cheese sauce! Add 4 tbsp butter to a medium sauce pan. Place the pan on the stove over medium heat. Once the butter is melted, whisk in 4 tbsp all-purpose flour. Whisk for about 30 seconds, just long enough to lose the raw flour taste but not long enough for the flour to caramelize. Add the thyme, rosemary, sage and red pepper flakes. Continue stirring to allow the herbs to saute for about 30 seconds. Slowly pour in the warm milk while whisking continuously so the roux and milk incorporate smoothly with no lumps. (HINT: Sometimes removing the pot from the heat source while you stir in the milk will help reduce the possibility of lumps forming.) Allow the mixture to come to a low simmer, stirring occasionally, until thickened.
While waiting for the sauce to simmer, start the pasta. Liberally salt the pot of boiling water. The water should taste very salty for best results. Add the pasta to the water and cook for a minute or two less than the suggested time on the pasta package so that the pasta is very firm, because you will be baking it later and you don't want it to get too soft.
Once your sauce has reached simmer, stir in the chevre, cheddar and half (2 oz) of the parmigiano reggiano cheeses. Add truffle oil and slowly stir until the sauce is smooth, with all cheese melted. Remove from heat. Add salt and pepper to taste.
In a small mixing bowl combine remaining parmigiano reggiano and panko.
Remove the pasta from heat and strain immediately making sure it is well drained. Return to empty pot or use a large mixing bowl to toss the pasta, cheese sauce and mushrooms. Place mixture in a deep glass or ceramic loaf pan, spreading evenly. Sprinkle the Panko/cheese mixture over the top, coating evenly. Bake on upper shelf of the oven for 15 to 20 minutes, or until the top is golden brown and cheese sauce is bubbly. Remove from oven and allow to sit for 10 minutes, then serve and enjoy the best mac & cheese you'll ever eat!