Heat a large skillet over moderate heat until hot enough to evaporate a bead of water on contact. Add the Szechwan peppercorns and stir until toasted and fragrant, 2 to 3 minutes. Adjust the heat so the peppercorns brown without scorching.

Combine the peppercorns and all of the remaining ingredients in a heavy, non aluminum 1 to 1 1/2 quart saucepan. Rest a deep-fry thermometer on the rim of the pot. Over moderately low heat, bring the mixture to a bubbly 225 degrees, stirring occasionally. Let simmer for 15 minutes, checking to ensure the temperature does not rise. Remove from the heat and let stand until cool or overnight.

Strain the oil through a fine-mesh sieve and discard the solids. Store the oil in an impeccably clean glass jar at cool room temperature.

This oil is particularly good for salads. Its herbal quality also makes it a nice partner to poultry or beef dishes.