Peel and seed the butternut squash and cut it into 1.5 inch chunks.
Cut the onion in half lengthwise, then cut into 1/4 inch slices.
Cut the tops off the beans and cut each in half on the diagonal.
In a large wok, heat the oil over medium high heat.
Add the curry powder, coriander, cumin, and chili flakes. Sauté the spices briefly in the oil, then add the onion, fresh ginger, garlic, lime zest and lemon grass. Continue cooking until the onions are soft.
Add the coconut milk, lime juice, soy sauce, fish sauce, and sugar. Bring to a simmer and taste. Adjust seasonings as needed.
Add the butternut squash and cook until it is tender, about 20 minutes.
Stir in the green beans and cook just until they are crisp tender, about 3 minutes.
Serve curry in bowls over basmati or jasmine rice garnished with chopped peanuts.