How to Make It
In a mini food processor, combine the onion, garlic, lemongrass and ginger and process to a paste. In a large skillet, heat the vegetable oil. Add the onion paste to the skillet and cook over moderately low heat, stirring occasionally, until browned, about 25 minutes.
Add the ground coriander, sugar, ground fennel seeds, cumin, turmeric and salt to the skillet and cook over moderately high heat, stirring, until fragrant, about 1 minute. Scrape the spice paste into a bowl and let cool completely.
In a large, shallow dish, coat the shrimp with the spice paste. Cover and refrigerate for at least 3 hours or overnight.
Soak 30 bamboo skewers in water for 30 minutes. Light a grill. Thread 1 shrimp lengthwise onto each bamboo skewer and stretch each one out on the skewer. Grill over high heat for about 1 1/2 minutes per side, until the shrimp are nicely charred and just cooked through. Transfer the shrimp skewers to a platter, and serve immediately with the Garlic Peanut Sauce.