For mashed potatoes you need starchy ones. I love Russets potatoes. They make the lightest, fluffiest mashed potatoes. Yukon gold is another type of starchy potatoes. I prefer Russets potatoes or a combination of both.

Ingredients
3 lbs Russet and/or Yukon Gold potatoes quartered
1/2 cup butter, room temperature
1/2 cup heavy cream, room temperature
6 oz mascarpone or cream cheese, room temperature
1/2 teaspoon salt
1/4 teaspoon pepper
6-8 slices of bacon, cooked and crumbled
3/4 cup shredded cheddar or gouda cheese
1/2 cup grated Parmesan cheese

Instructions
Place potatoes in a large saucepan filled halfway with salted water (make sure there's around 1 inch of water covering the potatoes).
Bring to a boil. Reduce heat; cover and cook for 10-15 minutes or until tender. Drain.
With a potato ricer or a masher mash the potatoes. Add the mascarpone or cream cheese, butter and cream; beat until blended.
Season with salt and pepper.
Stir in the crumbled cooked bacon, 1/2 cup cheddar or gouda cheese and 1/3 cup Parmesan cheese.
Heat the oven to 350F.
Transfer the mashed potatoes to a 2 qt casserole. Sprinkle with remaining cheeses. (you can reserve 2-3 tablespoons crumbled bacon to sprinkle on top as well)
Bake in the preheated oven for 20-25 minutes or until heated through.

Notes
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