01 - Place the peeled and diced potatoes in a large pot. Cover with salted water and bring to a rolling boil over high heat. Reduce to a simmer and cook for approximately 15 minutes, or until the potatoes are easily 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. Remove from heat and set aside.
03 - Drain the cooked potatoes thoroughly in a colander, then return them to the pot. Mash vigorously until smooth and free of large lumps.
04 - Pour in the milk and add the sour cream and shredded cheddar cheese to the mashed potatoes. Stir continuously until the mixture becomes creamy and the cheese has begun to melt evenly throughout.
05 - Gently fold in the sautéed bell pepper mixture, sliced green onions, ground cumin, smoked paprika, chili powder, salt, and pepper. Combine until all ingredients are evenly distributed.
06 - Taste the mashed potatoes and adjust the salt, pepper, or spices as needed to suit your preference.
07 - Transfer the finished mashed potatoes to a serving bowl. Garnish with freshly chopped cilantro if desired, and serve immediately while hot.