Place the potatoes in a large pot of boiling water for 15 minutes, or until fork tender.
While the potatoes are boiling, add the butter, garlic, black pepper, steak seasoning, kosher salt and rosemary to a small skillet on the stove over medium heat until the butter is melted.
Once the butter is melted, turn the temperature down to low and allow the flavors to combine for 5-10 minutes.
Once the potatoes are fork tender, drain the potatoes then return them back to the pot over low heat. Use an electric hand mixer to mash the potatoes, then hand mix in the garlic rosemary butter and half of the blue cheese.
Spoon the mashed potatoes into an oven safe bowl or casserole dish and sprinkle the remaining blue cheese on top.
Place in the oven and bake for 5-7 minutes.
Notes
This recipe serves 6-8 people as a side dish. If you want to double this recipe to serve 12-15 people at a holiday meal, simply click the 2X button above. The ingredient amounts will automatically update for the new serving size.
Store mashed potato leftovers in an airtight container in the refrigerator for up to 6 days.
To reheat them in the microwave, scoop a single portion of mashed potatoes onto a microwave-safe plate, or into a bowl, microwave for 1 minute, then stir in 1-2 tablespoons of milk or heavy cream and reheat for another minute.
To reheat them in the oven, place the mashed potatoes in an oven-safe dish. Cover with foil and place in a 350°F oven for 15-20 minutes. Remove and stir in 2-4 tablespoons of milk or heavy cream before serving.