Saute Veggies: Heat oil in a pot over medium heat. Add leeks and sauté for a few minutes until softened. Add yams, cabbage, bell pepper and snap peas and sauté over medium-high heat for 2 minutes. Reduce heat to medium and add ginger, garlic and curry paste and sauté for 3 minutes. Add chicken, if using.

Simmer: Stir in chicken broth. Mix cornstarch with the coconut milk, and then add to the pot. Bring to a simmer and cook for 15 minutes or until the potatoes are tender (and chicken is cooked through).

Fry Shallots: Meanwhile, add 3 Tablespoons oil and sliced shallots to a small skillet. Cook over medium heat, stirring gently the entire time, for several minutes until they begin to get golden. Once they start to get golden brown, remove to a paper towel lined plate and set aside.

Finish Curry: To the curry, stir in fish sauce, brown sugar, lime juice (and shrimp, if using). Simmer 5 more minutes. Stir in Thai basil leaves.

Serve: Top with fresh cilantro leaves and fried shallots before serving. Serve as a soup, or serve over hot cooked jasmine rice, cauliflower rice, zoodles, or cooked spaghetti squash.