Season the chicken thighs with salt and pepper.
Heat olive oil in a large skillet over medium-high heat.
Sear the chicken thighs skin-side down until golden, about 5-7 minutes.
Remove the chicken and set aside, draining excess fat as needed.
Add minced garlic to the skillet and sauté for 1 minute until fragrant.
Sprinkle the flour over the garlic and stir to form a roux.
Slowly whisk in chicken broth and bring to a simmer.
Return the chicken to the skillet, skin-side up, and cover.
Let the chicken simmer in the gravy for 25-30 minutes until cooked through.
Meanwhile, boil the cubed potatoes until tender.
Drain the potatoes, then return them to the pot for further drying.
Mash the potatoes, then stir in milk, butter, and cheese until smooth.
Adjust seasoning for the mashed potatoes and gravy as needed.
Serve the chicken atop the cheesy mashed potatoes, drizzling with garlic gravy.