Peel and cut the potatoes into a large dice. Place in a pot, fill with enough water to cover the potatoes completely, about 2 inches above, and bring to a boil. Cook until the potatoes are fork tender, when a fork goes in rather smoothly and easily. While the potatoes cook, roast the garlic. Place the peeled garlic cloves onto a sheet of aluminum foil. Drizzle with the olive oil, and season with a pinch of salt and freshly cracked black pepper. Wrap the sheet of foil around the garlic, like a package. Repeat the folding process with another sheet of foil, to prevent dripping. Place in the oven and roast for about 25-30 minutes.

Once the potatoes are soft, drain. Put them back in the pot, add the butter and mash together. Slowly add the buttermilk, 1/4 cup at a time, you might not need the full cup of buttermilk. Keep adding the milk until the potatoes are smooth and creamy, or desired consistency is reached. Season with salt and black pepper. Mince the chives, add it to the potatoes and mash once more.

When the garlic is done roasting, remove the package from the oven and allow to cool, slightly. Open the foil and add the cloves, with the oil into the potatoes. Thoroughly mash and smash the cloves into the potatoes. Taste to see if it is okay with salt and pepper, add more if needed. Set the potatoes aside while you make the filling.

Heat a large dutch oven, or pot, over medium-high heat. Add the oil and the ground beef. Cook the ground beef, constantly breaking down the meat with a spoon. Allow the meat to brown and cook completely. Once the beef is browned, add the chopped onion, carrots, and garlic to the pot. Cook until they are translucent and soft. Add the chopped mushrooms and continue to cook, stirring occasionally.

Add the thyme leaves, bay leaves, salt and pepper to the pot. Stir once again to mix evenly and continue to cook for another 5 minutes. Throw in the tomato paste and break it down into the meat and veggies. Sprinkle the mixture with the flower and allow it to cook for 3-4 minutes.

Pour in the guinness and scrape down the bottom of the pan, loosening the pan drippings. Add the worcestershire sauce, and beef stock. Cook until the sauce has thickened and somewhat reduced. Lastly, throw in the peas and mix well. Remove from the heat.

Pour the meat filling into a 9x13 baking dish, no need to grease or butter. Spread out the mixture evenly. Grab the mashed potatoes from earlier and scoop it onto the top of the beef. Evenly spread out the potatoes, completely covering the beef. Place in the oven and cook for about 20-25 minutes or until the top is lightly browned and crispy. Remove from the oven and sprinkle the shredded cheese, evenly on top of the potatoes. Place under the broiler for 3-5 minutes, until the cheese has melted and browned. Watch it carefully as the broiler can burn things rather quickly.

Remove from the oven and let it cool slightly before serving. Serve with Irish Soda Bread, or with a salad, if desired. Enjoy!