1 1/2 pounds yellow new potatoes, about 1 to 1 1/2 inches in width
1 tablespoon extra-virgin olive oil
1 teaspoon ground cumin
2 tablespoons unsalted butter, melted
2 garlic cloves, peeled and grated
2 tablespoons tamarind paste (not concentrate)
1 tablespoon date syrup, honey or maple syrup
1 teaspoon lime juice
1 medium shallot, peeled and minced
2 scallions, white and green parts thinly sliced
2 tablespoons chopped cilantro
1 green chile, such as a serrano or Thai chile, minced (optional)
Heat oven to 425 degrees and place a rack in the top third of the oven.
Scrub the potatoes under running water to remove any grit or dirt. Slice the potatoes in half lengthwise and place them in a medium saucepan. Fill the saucepan with enough water to cover them by 1 inch. Stir in 1 teaspoon salt and bring the water to a boil over medium-high heat. Boil for another 6 minutes until easily pierced with a sharp knife but still firm.
Drain the water and place the potatoes in a large mixing bowl. Season with salt. Drizzle the oil and sprinkle the cumin over the potatoes, and toss to coat well. In a roasting pan or baking sheet lined with aluminum foil, spread the potatoes out, cut-side up. Roast on the upper rack of the oven, flipping halfway through roasting, until they turn golden brown and crispy, about 35 minutes.
As the potatoes cook, mix the butter and garlic in a small bowl. Two or three minutes before the potatoes are done, pour the butter-garlic mixture over the potatoes and turn off the oven. Return the pan to the oven to cook in the residual heat for 2 to 3 minutes, being careful not to let the garlic burn. Remove the pan from the oven, and transfer the potatoes to a serving bowl.
In a small bowl, mix the tamarind paste, date syrup and lime juice. When ready to serve, pour the mixture over the potatoes and toss to coat well. Top with the shallots, scallions, cilantro and green chile, if using. Serve warm.