Salmon is a really unique fish that we often take for granted. Everyone smothers it with heavy sauces or encrusts it with this and that...which is fine. But why not enjoy the fish for what it is from time to time? So, simply season the salmon fillet with a nice sprinkle of salt and coarse ground pepper, both sides. Rub the fillet with a small amount of olive oil. Grill or pan sear the salmon until just medium rare or medium, about 2 to 3 minutes per side. (The saying is, you don't cook salmon, you should merely threaten it!)
In a skillet over high heat, heat the butter until nearly smoking. Add the shiitakes and leeks and cook on high heat until the edges just begin to brown, about 4 to 5 minutes. Season with salt and pepper.
To serve, simply spoon the mushroom/leek mixture onto salmon. Serve with a side of spinach spaetzle and a simple red pepper compound butter.