Preheat oven to 400F and lightly grease a large sheet pan.
Prick potatoes several times with a fork and place on sheet pan. Bake potatoes at 400F 55-60 minutes or until very tender. Remove from oven and cool slightly. Keep oven on.
Once potatoes are cool enough to handle, thinly slice the top off and scoop out potato, being careful not to break the bottom skin. Set mashed potato aside and save for another use. Place potato skins back on sheet pan and set aside.
In a large saucepan over medium-high heat, heat oil until shimmery. Add onion, carrots, chicken, and garlic to pan and saute several minutes until chicken is no longer pink and vegetables are crisp-tender.
Reduce heat to medium and stir in flour. Slowly add milk and cream, stirring until smooth. Bring sauce to a low simmer, stirring occasionally until bubbly and thickened.
Remove sauce from heat and stir in peas and season with salt and pepper to taste. Fill potato skins with chicken pot pie filling and top each potato with shredded cheese.
Bake potatoes at 400F 15-20 minutes until filling is bubbly and cheese is melted. Top potatoes with fresh parsley or chives and serve warm.