Peppered Filet Mignons with Mushroom Bourbon Sauce

This is the first recipe I've tried from Steven Raichlen's BBQ USA, though I have tried many recipes from his How to Grill book. I've made it twice now, and it's come out great both times. It goes really well with the grilled asparagus. Serve with a big fat Cabernet Sauvignon or a hearty Zinfandel.

Mushroom Bourbon Sauce:

12 oz. mushrooms
3 tbsp. butter
2 shallots, finely chopped (6 tbsp.)
1/2 cup dry white wine
3/4 cup beef or chicken stock
1 cup heavy (whipping) cream
2 tbsp. bourbon
1 tsp. Dijon mustard
Course salt and freshly ground pepper

Steaks:

4 large filet mignons (the ones I get aren't huge but they are thick)
2 tbsp. Dijon mustard
2 tbsp. cracked black peppercorns
2 tbsp. cracked white peppercorns
Course salt and freshly ground pepper

Cooking:

Trim the ends of the mushroom stems. Wipe the mushrooms clean with a damp paper towel (don't rinse them). Pick out 4 of the largest, best-looking mushroom caps and cut the stems off at the base. Thinly slice the rest of the mushrooms. Melt the butter in a heavy saucepan over medium heat. Brush a little of the melted butter (1 tbsp.) over the mushroom caps and set them aside.

Add the shallots to the saucepan and cook until soft and translucent, but not brown, about 3 minutes. Increase the heat to high and add the slices mushrooms until they are nicely browned and the mushroom juices have evaporated, 3 to 5 minutes. Stir in the wine, bring to a boil, and let boil until liquid is reduced by half, 3 to 5 minutes. Stir in the stock, bring to a boil, and let boil until reduced by two-thirds, 3 to 5 minutes. Stir in the cream, bring to a boil, and let boil until reduced by one-third (the sauce should be thick and creamy), 4 to 6 minutes. Add the bourbon, bring to a boil, and let boil for 1 minute. Whisk in the mustard and season with salt and pepper to taste; the sauce should be highly seasoned. Set the sauce aside while you prepare the steaks.

Brush each filet mignon on all sides with the mustard. Combine the peppercorns and 1 tbsp. salt in a shallow bowl and stir to mix. Thickly crust the steaks with the peppercorn mixture, concentrating it on the tops and bottoms and patting it into the meat with your fingertips.

Get your grill fire ready for direct grilling. Brush and oil the grill grate. Place the filets on the hot grate, and grill 4 to 6 minutes per side for medium-rare, or 7 to 8 minutes per side for medium.

Plate the filets. Reheat the sauce if necessary, and spoon over the filets. Top each with a mushroom cap and serve.