You don't have to serve red wine with steak, that's just what we've been taught. Most red wines tend to pair really well but what if you could serve white wine with steak—what would you serve? Filet is a more tender cut of beef, and when covered with a mustard sauce, it actually works with a richer white wine. I've found the mustard notes don't always compliment dried cherry or red fruits found in many reds. Would you ever put mustard on a cherry? If not, that's an argument against many Cabernet based wines.
Enter Chateau Musar Blanc stage right. Serge Hochar has been making wines sustainably in Lebanon since the 1950's waaaay before it was trendy. High up in the Bekaa Valley, Serge and his sons quietly (or not so quietly) make some of the most intriguing wines in the world. Most wine geeks and collectors could tell you about their first "Musar moment". Serge will tell you his whites are actually his reds. He makes his wine wine to age for years before it's ready to drink. The Musar Blanc is made from Merwah (distant relative of Semillon) and Obaideh (distant relative of Chardonnay) and oooooh momma, when you get a bottle, you won't forget it. A properly aged Musar Blanc will have enough body to stand up to the beef, but the flavors of the wine are more complimentary to the mustard cream sauce. And because it's a cream sauce, you want acidity in the wine to "cut through" the sauce, and this baby has it.