Cut the bacon into small cubes, the mushrooms into thick slices (about 1/4-inch or 5mm), dice the onion, press the garlic through a garlic press.
Heat 1 tablespoon of oil in a large frying pan over medium heat. Add the bacon and cook it for a couple of minutes or until golden and most of the fat is rendered.
Add the onion and cook, stirring from time to time, for about 4-5 minutes or until soft.
Add the garlic and thyme, cook for 30 seconds.
Transfer the content of the pan to a plate.
Cook the mushrooms in two batches: add the remaining 1 Tbsp of oil and 1 Tbsp of butter, increase the heat to high and add the first batch of mushrooms, spread them in an even layer. Don't stir the mushrooms for 1-2 minutes letting them brown then stir the mushrooms and cook them for 3-4 minutes until they released liquid and it's almost evaporated. You want the mushrooms browned and tender but not too soft. Transfer the mushrooms to a plate and repeat with the remaining mushrooms.
Add the mushrooms and bacon with onions back to the pan.
Add the flour and cook, stirring, until it has been absorbed by the mushrooms and no white streaks are visible.
Add the white wine. Cook, stirring, for 1-2 minutes or until the wine is almost evaporated.
Add all the remaining ingredients for the mushroom sauce: broth, soy sauce, milk, cream, lemon juice, Dijon mustard, and nutmeg.
Cook for 2-3 minutes or until the sauce is thickened. It should be thickened but can't be too thick or completely runny. If the sauce is too runny, cook it a little bit longer, if it's too thick, add some more broth to it. The sauce is the right consistency when you can draw a path across the back of the spoon. Season the sauce with salt and pepper.