Make a small mountain of flour and create a hole in the middle. Crack the egg and whisk with a fork while slowly putting flour in. By hand mix more flour until the dough becomes like play doh so not sticky (its ok to not use all the flour but leave for when rolling out the dough later) Knead for 10 minutes (!) to make rhe dough elastic and firm and get the gluten out. Make a ball and tightly wrap in plastic. Let is sit for 30 minutes at room temp.
Chop all the mushrooms of your choice (used leftover shiitake and oyster shrooms)
Roll out the dough in a rectangle shape. Make it as thin as possible. Use the leftover flour to keep it from sticking. When done fold the dough (dont press the edges of the folds!) 4 to 5 times and cut off small half cm slices to create the tagliatelli.. Unfold the cut off slices and add some flour to keep them from sticking together.
cook the tagliatelli in boiling water with a pinch of salt (optional add some olive oil) for about 3-5 minutes until al dente
Saute the garlic and add the mushrooms and parsley. Drain the tagliatelli and mix in with the mushrooms. Add pesto (or olive oil). Mix well and serve with shredded pecorino or parmezan.