1. 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.
2. 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.
3. In a large, shallow dish, coat the shrimp with the spice paste.
Cover and refrigerate for at least 3 hours or overnight.
4. 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
1½ 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 peanut sauce.
MAKE AHEAD The spice paste can be refrigerated for up to 2
days. Bring to room temperature before using.