Peel the potatoes and boil them in salted water until tender. Drain the potatoes and let them cool slightly, then add in the lukewarm milk and softened butter. Mash the potatoes and season them with freshly ground nutmeg and salt.
Put the thyme, rosemary, dried basil, paprika, salt & pepper in a mortar. Use a pestle to grind up the spices and mix them together. Rub the spice mixture into both sides of each of the chicken thighs.
Fry the seasoned chicken thighs in olive oil until golden brown on both sides, then remove the chicken thighs from the skillet and set them aside for later.
Melt the butter in the hot skillet you used for frying the chicken and sauté the garlic and onion in it. Add in the flour and let it cook briefly, then deglaze the pan with the chicken broth and heavy cream. Bring the sauce to a boil, stirring constantly, then let it simmer for about 10 minutes.
Stir in the grated parmesan cheese, chopped parsley, and chopped basil. Place the seasoned chicken thighs in the creamy garlic & herb sauce and let them cook for about 10 minutes. To serve, spoon a large scoop of mashed potatoes onto each plate, place the chicken on top, and cover the entire dish with creamy garlic & herb sauce.