1½ tsp. ground turmeric
7 shallots, roughly chopped
4 cloves garlic, roughly chopped
2 red or green Thai chiles, minced
1 3" piece ginger, peeled and thinly sliced
2 large fresh stalks lemongrass
3 tbsp. peanut oil
2 tsp. sugar
1 tsp. kosher salt, plus more to taste
1 14-oz. can unsweetened coconut milk
2 lbs. collard greens, stemmed and cut crosswise into ½"-wide strips
Freshly ground black pepper, to taste