Reverse-Seared Beef Tenderloin with Horseradish-Cheddar Sauce

Ingredients

• 1/4 cup black sesame seeds
• 1 tablespoon poppy seeds
• 2 tablespoons black peppercorns (if using a food processor, not a spice grinder, make sure you smash with a mallet first)
• 1 teaspoon brown mustard seeds
• 1/4 cup kosher salt
• 2 tablespoons dark brown sugar
• 1 teaspoon dehydrated onion
• 1 teaspoon granulated garlic
• 2 (12-ounce) cans evaporated milk
• 2 tablespoons hot sauce
• 1½ tablespoons Dijon mustard
• 8 ounces fontina cheese, freshly grated
• 8 ounces extra-sharp cheddar cheese, freshly grated
• 1 tablespoon cornstarch
• 1/4 cup prepared horseradish
• kosher salt, to taste
• 1 center cut beef tenderloin, trimmed (about 2 to 3 pounds)
• 1 teaspoon freshly ground black pepper
• 2 tablespoons olive oil
• 1/2 stick unsalted butter
• 4 cloves garlic, crushed
• 4 sprigs thyme