For the mushroom broth, add dried mushrooms and 500g water to sauce pan, bring to a boil, reduce heat to med-low and simmer for 5-10 minutes. Remove from heat and allow to seep for 10-15 more minutes.
Preheat a large saute pan over med-high and add a squeeze of olive oil and butter. When butter has melted, add fresh sliced mushrooms and a generous pinch of salt (about 5-6g). Stir to combine and cook for 5-6 minutes, stirring occasionally.
At this point, the fresh mushrooms should be about halfway cooked. Add shallots, garlic, thyme, and pinch of salt. Stir and cook for another 3-4 minutes. Add in about ½ of the dried mushroom broth (liquid only) to deglaze. Cook and reduce until fully evaporated and shallots are tender, about 3min. Add cream, bring to a simmer, and reduce by about half.
Bring a large pot of water to a boil over high and salt heavily. Add pasta to water and cook to al dente. Drain off pasta and add it to the mushroom cream sauce pan.
If the mixture is dry, add additional mushroom broth, about 100-150g. Toss and stir to combine.
Off heat, add grated parmesan, black pepper, and a small squeeze of lemon juice. Toss to combine. Adjust consistency with more parmesan if it's too thin or with mushroom broth if it's too thick.
Taste and add salt if needed. Garnish by topping with a sprinkle of parmesan, black pepper, and minced chives.