01 - Place the diced potatoes in a large pot and cover with salted water. Bring to a boil over high heat, then reduce to a simmer. Cook for approximately 15 minutes until the potatoes are fork-tender.
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 softened, then remove from heat.
03 - Drain the cooked potatoes thoroughly in a colander and return them to the pot. Mash with a potato masher until smooth and free of large lumps.
04 - Add the milk, sour cream, and shredded cheddar cheese to the mashed potatoes. Stir until the mixture is creamy and the cheese begins to melt.
05 - Gently fold in the sautéed pepper mixture, sliced green onions, ground cumin, smoked paprika, chili powder, salt, and pepper. Stir until evenly distributed.
06 - Taste the mashed potatoes and adjust salt, pepper, or spices as needed to suit your preference.
07 - Transfer to a serving bowl and garnish with freshly chopped cilantro if desired. Serve immediately while hot.