From one filet mignon lover to another, who also doesn't like mushrooms, the two worst filet mignon I've ever had in my entire life were at Le Cellier. Sorry, but it's truth.
The first time I tried the mushroom one and asked them to leave the mushrooms off, so it came out plain but it was a terrible piece of meat. The second time I went to Le Cellier I tried their other filet mignon. It had a maple BBQ glaze and while that might've tasted fine on a piece of chicken or other cut of meat, it was terrible on filet mignon and still it was not a good piece of meat.
I don't know if I just got stuck with 2 bad pieces of meat on my two different trips to that restaurant or not, but I won't be going back. QUALITY filet mignon should not need to have anything on it. By it's nature it's an excellent, flavorful, tender cut of beef, but I have no idea what it was with the two I had. Maybe they were overcooked or something, I don't know...
Having said that, I know that most people RAVE about Le Cellier, and I do love everything else about the restaurant. LOL
I just had to share my experiences. I'll be curious to hear how you like it