• Before you begin, rest and bring the sirloin roast to room temperature (about 45 minutes).
• Peel the garlic cloves and place into the center of a square of foil. Drizzle with olive oil and season with a pinch of salt. Close foil and place into the oven as it preheats to 250°F.
• Season steak with salt, garlic salt, pepper, oregano, and minced onion.
• Place roast into a pan and into the oven on the center rack. Cook for 1 hour. 
• Remove the garlic and steak. Brush the steak with Dijon mustard and ½ of the roasted garlic. Sprinkle parmesan cheese generously over the top. Place the steak back into the oven for 55 minutes. 
• Turn off the oven and let the roast rest inside the oven as it finishes cooking and comes to temperature.
• Remove the steak from the oven and place onto a wooden cutting board. Let rest 10 minutes. Slice steak and serve with mashed potatoes

mashed potatoes

• Add quartered potatoes (skin on) to a large pot and fill with water until the potatoes are just covered. Bring to a boil and boil for 15 minutes. 
• Add milk, heavy cream, butter, and reserved roasted garlic to a saucepan over medium heat.
• Remove the potatoes from the water and into a large bowl. Lightly mash.
• Once the saucepan starts simmering, pour it into the bowl with the potatoes and stir until combined Season lightly with salt and pepper to taste.