In a large saucepan, cover the Russet potatoes with water and add a dash of salt. Bring the water to a boil, then simmer until the potatoes are cooked through - approximately 15 to 20 minutes. Remove from water and pat dry. Optional: Remove skin if you prefer your mashed potatoes without skin.
In a separate pot, combine the milk and sugar and simmer, stirring often, until the liquid has thickened.
While potatoes are cooking, blanch the jalapeños by dropping them in the simmering water with the potatoes for approximately 1 to 2 minutes. Remove the jalapeños from the water, then skin them and mash the chilies into a paste.
Mash the potatoes using a fork while adding in the milk and butter. Add sour cream to reach your perfect mashed potato consistency. Finally add in jalapeño paste little by little, stirring and tasting often to get the right heat for you.
Top with chives and serve.