Place potatoes in a sauce pan, generously covered with water and add salt.

Cover bring to a boil, reduce heat to low and simmer until potatoes are tender when pierced with tip of knife tender, 20-30 minutes.

While your potatoes cook, make rajas.

Preheat your broiler

Place poblanos on sheet pan and broil until poblanos are charred on all sides.

Remove from broiler cover with dish towel and allow to steam for about 5 minutes. (Makes it easier to remove charred skin)

Remove charred skin, stem and seeds. Cut into rajas (strips)

Melt butter in a large sauce pan over medium heat.

Add flour, whisk to combine and cook for about 2 minutes.

Slowly whisk in warm milk, until thick. About 6-7 minutes.

Remove from heat and add cheese. After cheese has melted add rajas and stir to combine.

Season to taste and keep warm.

Drain potatoes well and mash with a potato masher.

Add rajas to mashed potatoes. Add more milk if needed.

Season to taste.