Place peeled and chopped Yukon Gold or Russet potatoes in a large pot, covering with cold water by about 2.5 cm. Stir in kosher salt and bring to boil. Cook for 15-20 minutes until fork-tender. Drain and return to pot to steam off moisture for 1-2 minutes.

While the potatoes steam, warm milk in a saucepan. Add unsalted butter to hot potatoes and mash until smooth. Incorporate the warmed milk and optional sour cream or cream cheese. Season with salt and pepper.

Pat chicken breasts dry. In a bowl, mix kosher salt, black pepper, garlic powder, and onion powder. Sprinkle over chicken breasts, patting in the spice mix.

Heat a skillet and add olive oil and butter. Add the seasoned chicken and sear for 4-5 minutes per side until golden brown. Transfer to a plate covered with foil.

In another skillet, combine sliced carrots, unsalted butter, brown sugar, water or orange juice, salt, and pepper. Cook for 6-8 minutes until tender, then glaze.

In the same skillet used for chicken, melt butter and sauté shallot until translucent. Stir in minced garlic. Pour in white wine and simmer until reduced by half. Add chicken broth and heavy cream.

Stir in Dijon mustard and black pepper. Let simmer until thickened. Return chicken, spooning sauce over them. Simmer until chicken reaches 74 °C.

To serve, place mashed potatoes on plates. Nestle chicken beside or atop. Ladle sauce over both and serve glazed carrots on the side.