Heat olive oil in a large pan over medium-high heat. Add the onion and garlic, cooking for 3-4 minutes until softened. Add the chicken drumsticks and cook for 8-10 minutes, turning occasionally, until golden brown on all sides.
In a mortar, crush the Szechuan pepper with salt. Season the chicken drumsticks with this mixture.
Pour in half of the beer to deglaze the pan. Cover and simmer over medium heat for 40 minutes, until the chicken reaches an internal temperature of 74°C / 165°F.
Pour in the remaining beer and bring to a boil for 1-2 minutes.
Cut the parsley into fine strips and sprinkle over the chicken. Arrange on plates and serve immediately.