2 pounds dried black-eyed peas
1 sweet onion, such as Vidalia, peeled and halved through the root end (keep the root attached)
4 whole cloves
1 garlic head, cut in half
10 black peppercorns
2 dried bay leaves
1 chile de árbol or other small dried chile
1 cup olive oil
2 tablespoons kosher salt, plus more to taste
Hot sauce, to taste
Put the peas in a large bowl, add water to cover by 2 inches, and soak overnight.
Blacken the onion: If you have a gas stove, turn one burner on high and place the onion halves directly on the grates next to the flame and cook, turning occasionally, until the onion is charred on all sides, about 5 minutes. Otherwise, heat the broiler and broil the onion on a baking sheet a few inches from the heat, turning occasionally, until charred, 1 to 2 minutes. Set aside to cool.
When the onion is cool enough to handle, poke 2 cloves into each half, and add the onion to a large stockpot. Drain the peas, discarding the liquid, and then transfer the peas to the pot.
Place the garlic, peppercorns, bay leaves and chile on a 12-inch square of cheesecloth and wrap tightly, using twine to seal the packet.
Add 6 quarts water and the spice packet to the pot and bring to a boil over high heat. Skim any foam that collects on the surface, then reduce to a simmer. Stir in the olive oil and 1 tablespoon salt and cook, stirring and skimming occasionally, until the peas are fully cooked and the cooking liquid has thickened, 1 to 2 hours.
Discard the spice packet, season with the remaining 1 tablespoon salt (or to taste) and the hot sauce and serve.