Preheat oven to 375°F (190°C). Line a rimmed baking sheet with parchment paper.

Heat olive oil in a large skillet over medium heat. Add diced onion, carrots, and celery, cooking for 8-10 minutes until softened and lightly golden.

Add minced garlic and cook for an additional minute until fragrant. Remove from heat and cool completely.

In a small bowl, combine fresh breadcrumbs with milk, stirring until evenly moistened. Let stand for 5 minutes.

In a large mixing bowl, combine ground beef, cooled vegetable mixture, soaked breadcrumbs, beaten eggs, ketchup, Worcestershire sauce, salt, pepper, and thyme.

Using clean hands, gently mix ingredients until just combined, being careful not to overmix.

Shape mixture into a loaf approximately 9x5 inches and place on prepared baking sheet.

For the glaze, whisk together ketchup, brown sugar, vinegar, and Dijon mustard in a small bowl.

Brush half of the glaze over the meatloaf and bake for 30 minutes.

Meanwhile, place cubed potatoes in a large pot and cover with cold salted water. Bring to a boil and cook for 15-18 minutes until fork-tender.

After 30 minutes, brush remaining glaze over meatloaf and continue baking for 15-20 minutes until internal temperature reaches 160°F.

Drain potatoes thoroughly and return to the pot. Add softened cream cheese and butter, mashing until smooth.

Gradually add warm milk until desired consistency is reached. Fold in shredded cheddar cheese, salt, white pepper, and garlic powder.

Let meatloaf rest for 10 minutes before slicing. Garnish mashed potatoes with fresh chives.

Serve sliced meatloaf alongside generous portions of cheesy mashed potatoes.