01 - Place the peeled and diced potatoes in a large pot. Cover with generously salted cold water and bring to a rolling boil over high heat. Reduce to a simmer and cook for approximately 15 minutes, or until the potatoes yield easily when pierced with a fork.
02 - While the potatoes cook, heat a small skillet over medium heat. Add the diced red bell pepper, jalapeño, and minced garlic. Sauté for 3 to 4 minutes until the vegetables have softened and become fragrant. Remove from heat and set aside.
03 - Drain the potatoes thoroughly in a colander, then return them to the pot. Using a potato masher, work the potatoes until smooth and free of large lumps.
04 - Add the milk, sour cream, and shredded cheddar cheese to the mashed potatoes. Stir vigorously until the mixture is creamy and the cheese begins to melt into the potatoes.
05 - Gently fold in the sautéed pepper and jalapeño mixture, sliced green onions, ground cumin, smoked paprika, chili powder, salt, and black pepper. Stir until all ingredients are evenly distributed throughout the potatoes.
06 - Taste the mashed potatoes and adjust the salt, pepper, or chili powder as needed to suit your preference.
07 - Transfer the mashed potatoes to a warm serving bowl. Garnish with freshly chopped cilantro if desired and serve immediately while hot.