Wash and peel the potatoes, cutting them into about 1-2 inch chunks (be sure all the chunks of potato are the same size so they cook evenly).
Add the potatoes to a large pot and fill the pot with hot water just so the potatoes are covered. Add the garlic, thyme and salt, and stir well.
Set the pot over high heat on the stove and cover. When it reaches a boil, continue cooking, covered over medium heat for about 20 minutes or until the potatoes are fork-tender.
Preheat your oven to 425 degrees Fahrenheit.
Grease a large lasagna pan or casserole dish (slightly bigger than 9-inches by 13-inches), and set aside.
When the potatoes are done, drain the potatoes and remove the garlic cloves and thyme sprigs.
Add the potatoes back into the pot and mash well with a potato masher (by hand).
Add the butter, cream cheese, garlic powder and onion powder, and some salt and pepper (you can always add more salt and pepper later, so start with a few pinches of each) on top and replace the lid. Wait for a few minutes so the heat of the potatoes can warm up the other ingredients.
Use a hand mixer to mix everything together until the mixture is creamy and smooth, and everything is incorporated. Don't over-whip...this will create glue-y sticky mashed potatoes.
Spoon the mashed potatoes into the baking dish and smooth out the top.
Bake at 425 degrees Fahrenheit for about 20-25 minutes, or just until the top gets crispy and golden brown.