To make the boxty:

1. Peel 1 lb of of the potatoes (4-5 small/medium potatoes) and chop them into 1 inch pieces. Add them to a medium saucepan (I used a 3 quart size) and cover with water.
2. Generously salt the water and bring the saucepan to a boil. Allow the potatoes to cook for 30 minutes, or until you can pierce them with a fork and not feel resistance.
3. While the saucepan boils, prepare the grated potatoes. Use a box grater or fine shredding disc with a food processor to grate the potatoes. You should have about 1 1/2 cups.
4. Immediately rinse the shredded potatoes in cold water to wash away the extra starch. Use a fine mesh sieve to drain the potatoes. Continue to rinse them in cold water until the water runs clear from the sieve.
5. Squeeze out as much excess water from the potatoes as possible, and add the dry shreds to a large mixing bowl.
6. After the boiled potatoes are tender, drain them thoroughly and pass them through a ricer. Alternatively, use a potato masher to smooth them out. Set aside to cool slightly.
7. Preheat the oven to 200 degrees and line a baking sheet with a few layers of paper towel. Place a cooling rack on top the the paper towel and set aside to catch the finished pancakes.
8. Set a large skillet over medium heat and add 2 TB of olive oil. Allow the oil to heat up while you finish the boxty batter.
9. Scoop 1 1/2 cups of mashed potatoes into the bowl with the grated potatoes. Add the cheese, onion and flour. Whisk the egg into the milk until blended and pour into the bowl, along with the salt and pepper. Mix well until incorporated, the batter will flow a bit like thick lava, but should not be soupy.
10. Once the oil starts to shimmer and you can just barely see wisps of smoke, drop the batter into the skillet, 1/3 cup at a time. Use the bottom of the measuring cup or the back of a spoon the flatten the pancakes to about 1/4 inch thickness, or 6 inches across.
11. Fry the pancakes for about 3 minutes per side, working in batches of 2 pancakes. Add more oil between batches as needed, transferring the finished boxty to the prepared baking sheet.
12. After all the pancakes are done, transfer the baking sheet to the preheated oven to keep them warm and crisp while you make the gravy.

To make the gravy:

1. In the same hot skillet, add the sausages and cook for 2-3 minutes per side, until fully cooked through to a safe temperature of 145 degrees. Remove the sausages to a paper towel lined plate and set aside to rest.
2. Add the onions and mushrooms to the hot fat in the skillet and cook, stirring occasionally, until the mushrooms have given up their liquid and started to sizzle, about 8 minutes. Add the garlic and thyme and cook for another minute.
3. Stir the Guinness, beef broth, brown sugar, mustard and Worcestershire sauce together and pour into the skillet. Slice the sausages and add back into the skillet and allow the gravy to come back up to a simmer. Cook for 10 minutes, stirring occasionally.
4. After 10 minutes, stir the cornstarch and water together to make a slurry, and whisk into the gravy. It will thicken up immediately. Remove the gravy from the heat.
5. Serve boxty hot with Guinness gravy. Store any leftovers in the fridge for up to a week, and freeze the boxty for up to 6 months.