01 - Place the diced potatoes in a large pot and cover with generously salted cold water. Bring to a rolling boil over high heat, then reduce to a gentle simmer. Cook for approximately 15 minutes until the potatoes yield easily when pierced with a fork.
02 - While the potatoes cook, warm a small skillet over medium heat. Add the diced red bell pepper, minced jalapeño, and garlic. Sauté for 3 to 4 minutes, stirring occasionally, until the vegetables have softened and become fragrant. Remove from heat and set aside.
03 - Once tender, drain the potatoes thoroughly in a colander. Return them to the still-warm pot and mash vigorously until smooth and free of large lumps.
04 - Pour in the milk and add the sour cream and shredded cheddar cheese. Stir continuously until the cheese has melted and the mixture reaches a creamy, uniform consistency.
05 - Gently fold in the sautéed pepper and jalapeño mixture, sliced green onions, ground cumin, smoked paprika, chili powder, salt, and pepper. Combine until the seasonings are evenly distributed throughout.
06 - Taste the mashed potatoes and adjust salt, pepper, or spice levels as desired to suit your preference.
07 - Transfer to a warm serving bowl, garnish with freshly chopped cilantro if using, and serve immediately while hot.