In a medium bowl, whisk together the broth, flour, nutritional yeast, mustard and soy sauce. Whisk until there are no clumps anymore. Set aside.
Remove the raw kernels from the corn cobs. Set aside. (see blog for visual explanation)
In a large pan, melt 1 tbsp of the butter on medium-high heat. Then, add the onions and cook for about 5 minutes or until soft. Add a little salt and pepper.
Then, add the remaining 2 tbsp of butter, mushrooms, garlic and thyme. Cook for another 7-10 minutes or until the mushrooms are soft and cooked through. Don't move them around constantly, give them some time to roast and brown in between stirring in the pan. This will help develop a deeper flavor.
Add the white wine and raw corn kernels. Cook until there is almost no liquid anymore but still moist, for about 3-5 minutes.
Add the broth mixture to the pan and bring to a low simmer while whisking often. Let the mixture cook, still on medium-high heat, until the sauce thickens. This should take about 5 minutes.
Remove from the heat and serve over pasta, brown rice or mashed potatoes. Enjoy!