Place a large pot of water over high heat. Season it well with kosher salt. Once boiling, drop in 4 oz of spaghetti. Once cooked to your preferred doneness, remove it from the pot, reserving about ½-1 cup of pasta water.
With a sharp knife, thinly slice 2 pints of wild or mixed mushrooms. Set them aside. Thinly slice 1 large yellow onion, 4 cloves of garlic, and chop 5-6 sprigs of thyme. Set all that aside.
Place a medium pot over medium-high heat and add in 2 tbsp of olive oil. Once heated, add in your sliced onion, minced garlic, chopped thyme, and ¼ tsp of chilli flakes. Sauté for 4-5 min or until caramelised and soft.
Next, add your thinly sliced mushrooms. You want as much liquid to leach out of the mushrooms. Allow them to caramelise and soften, about 8-10 minutes. Season with 1 tsp of kosher salt and 1 tsp of black pepper. There should be a good amount of colour on the bottom of the pot; this is a great time to deglaze with ¼ cup of white wine. Give it a stir.
Once your mushrooms are nice and cooked down, add in 1 cup of heavy cream. Allow your cream sauce to reduce and thicken up (2-3 min). Add in your cooked pasta and give it a good mix. Slowly stream in ½ cup of your reserved pasta water and mix until the sauce is nice and creamy. Add in the juice of ½ a lemon, 1/2 a cup chopped parsley and season with kosher salt and more black pepper.
In a pan over medium heat, once heated, add in ½ cup of panko. Give it a stir and allow it to toast. Once golden brown, remove it from the pan and set it aside.
Garnish your pasta with grated parmesan, toasted panko, and more chopped parsley.
