Clean mushrooms with a damp paper towel. Washing them under water can make them turn slimey.
Heat a large skillet or frying pan on a low flame.
Cut the mushrooms to small bite size pieces without or without the stems.( If you do decide on using the stems, cut off the bottom third. It is usually drier and more fibrous than the rest of the stem).
Finely chop the shallot.
Add olive oil, shallots and mushrooms to the pan and increase to medium heat and cook for 5-7 minutes stirring occasionally until the mushrooms are still crunchy but not raw.
Add the chopped garlic and sauté for a minute.
Add the balsamic vinegar, mix well and simmer the vinegar liquid until it is nearly gone. The idea here is cook off the tangyness of the vinegar until it is sweet.
Stir in the half cup of the water from the boiling pasta, add half the marjoram and give a little stir.
On a very low fire finish off the mushrooms by quickly blending in cold butter one tablespoon at a time. You do this by using the tip of fork to gentle stir the butter through the mushrooms. You are not cooking but gently emulsifying the butter with the liquid.
Salt to taste.
Add the cooked Fregola, increase heat to medium and cook for a couple of minutes to allow the pasta to absorb the liquid and butter. If too dry add a little more pasta water.
Garnish with rest of herbs and serve with freshly grated Parmesan cheese