Place the cubed sweet potatoes in a large saucepan or Dutch oven and add enough water to cover by about 1″. Add 1 teaspoon of the salt and bring the mixture to a simmer over medium-high heat. Reduce the heat and simmer, uncovered, until the potatoes are tender (in other words, it’s easy to slide a fork in and out), about 9 to 12 minutes.

Drain well, then return the potatoes to the pot. Mash the sweet potatoes to your desired consistency.

Promptly add mayonnaise, and almost all of the green onion, reserving a small amount of each for garnish. Add the Mixed vegetables, all of the butter, and the remaining 1 teaspoon salt. Season to taste with additional salt, complete seasoning, and freshly ground black pepper.

Transfer the mashed potatoes to a serving bowl and swirl Sprinkle with the reserved green onion and parsley, drizzle the top lightly with olive oil, and finish with a sprinkle of pepper.

Serve promptly. Leftovers will keep well, covered, and refrigerated, for 3 to 4 days.