For the peanut sauce: Heat the peanut oil in a small saute pan over medium-low heat until hot. Add the onion and jalapeno and cook until softened and fragrant, about 5 minutes. Add the garlic and ginger and cook for 20 seconds. Then add the coconut milk, peanut butter and curry paste. Increase the heat to medium and whisk until the mixture comes together, 2 to 3 minutes. Turn off the heat and whisk in the lime juice, soy sauce and fish sauce. If the sauce separates before you are ready to serve, whisk it until it emulsifies and use immediately.
For the vegetables: Prepare a large bowl of ice water and set aside. In a large pasta pot fitted with a colander insert, bring water to a boil over medium-high heat. Add 3 tablespoons salt, then add the carrots. Cook for 1 minute, then add the cauliflower. Cook for 1 minute, then add the green beans and broccoli and continue to cook, 2 minutes. Remove the colander from the pot and drain of excess water. Carefully pour the vegetables into the ice water so that they're submerged. Line a sheet tray with paper towels. When the vegetables are cold to the touch, remove them to the paper towels. Dry the vegetables and then put them into a large, shallow serving bowl or on a platter.
Serve the blanched vegetables with the peanut sauce for dipping.