Combine flour, cold butter, and parsley using a pastry cutter, or use your hands to rub them until they form coarse bread crumbs texture, some small and some bigger lumps. Keep it chilled in the fridge. This needs to stay cold
Prepare the filling:
Preheat a large skillet with 2 Tbsp of oil over medium heat. Add the onion and saute for about 2 minutes until aromatic.
If you are using raw chicken, add the chicken pieces here and cook until the chicken is opaque. Remove the chicken from the pan and set aside. We'll add this back in later. If you are using leftover cooked chicken, omit this step
Add the red curry paste and saute for another minute.
Add the flour and saute for another minute.
Gradually add in the chicken broth and coconut milk and continue mixing until the mixture starts to thicken just slightly. Add the fish sauce and brown sugar. Stir to combine everything
Add the chicken and veggies and continue to cook for another minute. The sauce will thicken a bit more now but it shouldn't be overly thick either. We want to have some creamy sauce. Remove from the heat
Start preheating the oven to 350 F (180 C) for a conventional oven. If you have a convection oven, reduce the temperature by 20 F (15 C)
Back to the dumpling:
Whisk yogurt, milk, and egg until combined.
Remove the flour mixture from the fridge. Add the yogurt mixture into the flour mixture and very gently stir until just evenly moist. DO NOT overmix. As long as you don't see pockets of dry flour mixture, you are done mixing. It has a consistency like a very thick batter
Assembling:
Oil the bottom and sides of a 9 x 13 inch baking dish (about 3-quart capacity). Pour the chicken mixture into the dish. Scoop the dumpling batter by a spoonful, about 12 scoops evenly across the top, giving some space in between each scoop. It will spread during baking
Baking:
Put the dish in the middle rack and bake for 30-35 minutes or until the dumplings are cooked through and the sauce is bubbly. If you insert a toothpick into the dumplings, it should come out clean. The dumplings won't color much, with some spots with crisp edges
Serving:
Let it stand for about 5 minutes to settle and then serve warm
Notes
If you use raw boneless, skinless chicken breast or thighs, you will need about 700 grams (2 lbs) and cut into 1-inch pieces.
I use frozen green beans (thawed). You can use chopped broccoli florets, cauliflower, carrots, chopped kale, etc. Try to avoid any veggies that may let out too much liquid like zucchini for example