Peel the potatoes if you prefer your mashed potatoes without skin, then cut them into large chunks. In a large saucepan, cover the potatoes with water and add a dash of salt. Bring the water to a boil, then simmer until the potatoes are fork-tender, approximately 15 to 20 minutes. Drain well.

In a separate pot, warm the milk and sugar over low heat, stirring often, until the milk is steaming and the sugar has dissolved. Don’t let it boil.

While the potatoes are cooking, blanch the jalapeño halves by dropping them into the simmering water with the potatoes until they’re soft, about 5 minutes. Remove the jalapeños from the water, then mince or mash them into a fine paste. Peeling them is optional.

Mash the potatoes with a potato masher (or a fork) while adding in the warm milk and the butter. Add sour cream to reach your perfect mashed potato consistency, and season with salt and pepper. Finally, add in the jalapeño paste little by little, stirring and tasting often to get the right heat for you.

Top with chives and serve.