1. Grind peppercorns in an electric spice grinder (or clean coffee grinder) to a medium grind. In a small bowl, combine pepper, brown sugar, salt, ginger, allspice, nutmeg, coriander, cardamom, and cloves; whisk to combine. Rub meat sparingly with crushed garlic slivers, then rub all over with spice mixture.
2. Cut tenderloin crosswise in half. Wrap each half very tightly with several layers of plastic wrap (so that it looks swaddled), put in a rimmed pan, and refrigerate 4 days.
3. Preheat oven to 400°. Heat 1 tbsp. oil in a large frying pan (not nonstick) over high heat. Add 1 piece of meat and sear until well browned on all sides, 7 to 10 minutes. Transfer to a rimmed baking pan and repeat with remaining oil and beef. Transfer baking pan to oven and cook meat until an instant-read thermometer inserted in thickest part registers 135°, 20 to 30 minutes. (Halves may not cook at the same rate; after meat has been in the oven 20 minutes, begin taking temperature of both pieces of meat every 5 minutes.) Transfer to a carving board, tent with foil, and let rest 15 minutes. Remove kitchen twine.
4. Cut meat into very thin slices (less than 1/4 in., if possible) and serve warm or at room temperature, with crusty rolls and chutney if you like.
Note: Nutritional analysis is per 2-slice serving.
If you have whole spices instead of already ground, grind them along with the peppercorns in the amounts called for below. Many butchers will trim the tenderloin of excess fat and tie it as a roast for you, but you can also buy untrimmed, untied loins (they're usually cheaper) and do it yourself. Once you've trimmed off the fat with a sharp knife, tie the roast at 2-in. intervals with separate pieces of kitchen twine to give it an even shape as it cooks.