Preheat the oven to 375 degrees Fahrenheit. Massage the oil into the chanterelle mushrooms and spread out evenly on a roasting pan. Roast in the oven until the mushrooms are lightly golden at the tips and the mushrooms are a bit wrinkled, about 25 minutes. Puree with butter and salt until smooth. Cover and refrigerate. Use within 1 week.
Melt the butter in a large frying pan over medium heat. Add the mushrooms, oyster sauce, and soy sauce and cook until the mushrooms release their moisture and most of the liquid evaporates from pan, leaving a thick sauce that the mushrooms are cooking in, about 20 minutes, stirring every 5 minutes. Remove from heat and set aside.
Preheat the oven to 425 degrees Fahrenheit with a 10 to 12-inch cast iron skillet inside of it. In a large bowl, whisk together the flour, corn starch, thyme, garlic salt, and onion powder until combined. Set aside.
In the bowl of a stand mixer fitted with the whisk attachment, beat the eggs at medium high speed until frothy. Add the milk and continue whisking until combined. Switch to the paddle attachment and gradually add the flour mixing at low speed, scraping down the sides of the bowl as needed, until a smooth batter just forms.
Remove the skillet from the oven and add the butter to it, stepping away since it will splatter a bit at first. Quickly pour the batter into the pan and immediately place the pan back in the oven. Bake until the edges puff up and are deeply golden, about 16 to 18 minutes.
Once finished, add the chanterelle butter on top, then the creme fraîche, then the sautéed mushrooms. Sprinkle with the fresh thyme and serve immediately.