- For the Filling:
- 3 tablespoon unsalted butter
- 1/4 cup finely chopped shallots
- 10 ounces button mushrooms, cleaned and cut into 1/2-inch sliced
- 2 teaspoons freshly minced garlic (about 2 medium cloves)
- 1/2 teaspoon crushed red pepper
- 10 ounces frozen chopped spinach, thawed and squeezed dry
- Kosher salt
- Freshly ground black pepper
- 1 whole beef tenderloin, about 5 pounds, trimmed of silverskin and butterflied
- Type of fire: two-zone indirect
- Grill heat: medium
To make the filling: Melt butter in a 12-inch skillet over medium-high heat until foaming subsides. Add in shallots and cook, stirring occasionally, until softened, about 5 minutes. Add in mushrooms and cook, stirring occasionally, until well browned, about 7 minutes. Stir in garlic and crushed red pepper and cook until fragrant, about 30 seconds. Add spinach and cook until warmed through, about 2 minutes. Remove from heat and season with salt and pepper to taste.
Lay butterflied tenderloin opened flat. Season generously with salt and pepper. Spread filling over tenderloin, leaving about 1/2 an inch edge with no stuffing. Roll tightly into a cylinder and tie shut with butcher twine at 1-inch intervals. Season outside of beef generously with salt and pepper. Let rest for 45 minutes while preparing grill.
Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange the coals on one side of the charcoal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Clean and oil the grilling grate. Place tenderloin on cool side of grill, cover, and cook until an instant read thermometer reads 120°F degrees when inserted into the thickest part of the beef. Transfer beef to hot side of grill and cook until well browned, 2-3 minutes per side. Transfer to a cutting board and let rest for 15 minutes. Remove twine and cut into 1-inch slices and serve.