In a large pan (large enough to eventually hold the simmer sauce and the ingredient you will be simmering), heat the oil over medium heat. Add garlic, ginger, and red pepper flakes and cook for 2 minutes until fragrant. DO NOT OVERCOOK THE GARLIC.
Add the peanut butter and stir to combine. Add the soy sauce, pumpkin, and curry paste. Stir to thoroughly combine.
Once sauce comes together, turn the heat to low.
If you are cooking meat in the simmer sauce, add approximately 1 pound of meat, cut in bite size pieces. If you are cooking vegetables, have warm vegetables before combining them with the sauce (such as by steaming or microwaving). If you are using noodles, cook noodles in a separate pan and then add to the sauce.