In a large, deep sautee pan, fry the pancetta in the olive oil on a medium low heat until crispy. While that starts to fry, chop the garlic scapes (or garlic) and mushrooms.
When the water is boiling, salt the water well and add the dry pasta. Cook according to package instructions.
Slice the thick spine off the kale by folding the leaf in half along the spine to expose it and slice down. Stack several leaves together and roll the leaves up into a short, fat cigar to chiffonade it. To create shorter pieces that are easier to eat you can also slice the rolled up leaves in half lengthwise and then chop the two halves into strips.
When the pancetta is crispy turn up the heat to medium and add the mushrooms and garlic scapes. Let the scapes cook for 5 minutes. Add a splash more olive oil if needed to get the mushrooms coated so they fry nicely. Add a pinch of salt and pepper.
When the mushrooms have cooked down add the kale. Stir the kale with a spatula around the pan so that it can wilt. This will take about 1 minute.
When the kale is wilted add the salt, pepper, chili flakes, cream and creme fraiche (if using) . Stir to combine. Let it simmer for another minute and then turn off the heat.
Before draining the pasta, take about a cup of the pasta water out with a measuring cup.
When pasta is cooked al dente, drain the pasta and add it to the pan with the kale, mushrooms and sauce.
Stir it around so that all the pasta gets lightly coated with the sauce. Add some of the pasta water ¼ cup at a time until you get the desired consistency of the sauce. It is not a runny sauce that pools on the bottom of the pan. It should be sticking to the pasta and kale so don't add too much water. You will likely only need ½ cup but it is better to have a little extra on hand.
Serve with a generous amount of freshly grated Parmesan cheese.