The secret to the creamy, buttery interior of these roasted potatoes is par-cooking the halved potatoes before roasted. A quick marinade before and after with lemon, olive oil, salt, and garlic boosts flavor that is extra fabulous. Blanching the mint in the potato cooking water keeps it bright green. The combination of both fresh and dried mint is another way to boost flavor here.
Place a sheet pan on the center rack of the oven and heat to 400 degrees.
In a medium pot, cover the potatoes by about an inch with cool water. Add 1 tablespoon of the kosher salt. Bring the water to a boil over high heat, then reduce the heat and simmer until the potatoes are partially cooked through, about 5 minutes depending on the size of your potatoes. A knife inserted in a potato should push through, but with some resistance.
While the potatoes cook, hold the sprigs of mint top-side-down in the boiling water for 10 seconds. Blot the sprigs dry and pluck the mint from the stems. Dry again, and finely chop the mint.
While the potatoes cook, make the marinade. In a small bowl, whisk the olive oil, lemon juice, and 1/2 tablespoon of salt.
Drain the potatoes and place them in a medium bowl. Pour the marinade over the potatoes and combine. I like to use my hands for this to gently handle the potatoes and be sure they are well-coated. Allow the potatoes to rest in the marinade for 5 minutes, tossing them a few times in the marinade.
Remove the hot sheet pan from the oven. Immediately transfer the potatoes to the sheet pan using a slotted spoon. Set the bowl of marinade aside to be used shortly. Turn all of the potatoes cut-side down using tongs.
Return the sheet pan to the oven and roast for about 30 minutes, or until the cut sides are golden brown.
Remove from the oven and use a spatula to transfer the hot potatoes back to the bowl of marinade. Add the garlic and stir to completely coat the hot potatoes.
Transfer the potatoes to a serving dish and finish with the chopped blanched mint and mint salt. Serve immediately.