Step 3: Sauteing
1. Fry the onions in a little butter or olive oil on high to medium high heat. We want really nice brown bits to give the gravy that great roasted taste. Obviously avoid burning them. Onions have quite a bit of liquid inside them, so they can take a pretty high heat, but once they start turning brown, pay more attention and stir more often to minimize the chance of burning.
2. Add the garlic when the onions are close to done. Garlic burns easily on high heat, so this is when you want to turn down the heat to medium or medium low.
3. Add the mushrooms. They'll have a decent amount of liquid in them from the washing, so we want to cook them slowly to draw it out nicely for the sauce. This time I ended up adding one box of mushrooms first, then chopping and adding the second. This led to a nice gradation from totally cooked mushroom bits to fairly solid mushroom slices. If I weren't so lazy I might have cooked them longer, for a smoother gravy, but a few slices are nice too.
4. After the mushrooms have cooked down a little, add the thyme and paprika. I tend to sprinkle, mix, smell or taste, and repeat the process until I'm happy.
I'm horrible at estimating times for these steps, and it's more important to get it to the right doneness than check the time. But the onions might take 10 minutes, the garlic may take 1 minute, and the mushrooms another 10 minutes. But while the mushrooms are cooking, you can start the roux... (And if the mushrooms are done before the roux, you can take them off the heat until you're ready for them, or vice versa.)