No matter how hard I tried, I could never recreate the vivid, vivacious flavors of Thai curries at home. It wasn't until I was invited to a cooking class at the Thai Embassy in Los Angeles that I learned two of the secrets: "cracking" the coconut cream that accumulates at the top of the can of full-fat coconut milk (cooking out all the moisture so that the oil separates from the solids); and "blooming" the curry paste in the cracked coconut cream so that all those sleepy flavors of chiles and floral aromatics come back to life. With just these two techniques, my curries have gone from ho-hum to high-octane!
Add 1 cup water to an electric pressure cooker and add the rack. Put the kabocha squash on the rack and follow the manufacturer's guide for locking the lid. Set to pressure cook on high for 3 minutes. Follow the guide again for releasing pressure, then carefully remove the lid. Remove the squash from the pressure cooker and set aside until ready to use.
Heat a large skillet over medium-high heat and add the oil. Once the oil is hot, add the mushrooms and saute until lightly browned, about 10 minutes. Remove from the skillet and set aside until ready to use.
Set the same large skillet over medium-low heat. Carefully scoop the coconut cream (the thick, almost solid white stuff) out of the can of coconut milk into the skillet. Set aside the remaining liquid in the can. Cook the coconut cream until it resembles yogurt and is sizzling around the edges, about 5 minutes. Add the curry paste, ginger and garlic. Turn the heat up to medium. Saute until the paste has deepened in color and the oil starts to separate from the paste, 3 to 5 minutes.
Pour in the chicken broth, sugar, remaining canned coconut liquid and 1 teaspoon fish sauce. Taste; add more fish sauce if it's not salty enough. Stir well and bring to a boil. Add the squash, mushrooms and green beans. Stir well and turn the heat to low. Simmer until the green beans are cooked through, about 15 minutes.
Finish with the lime zest, a squeeze of the lime wedge and the basil. Serve over rice.