1-Step 1: Cook the Bacon Until Crispy Start by preparing the bacon, which adds that essential savory crunch to your casserole. Place 200 g (6 oz) of chopped streaky bacon in a cold non-stick pan over medium heat. There’s no need to add oil because as the pan heats up, the bacon fat will render out and create its own cooking medium. This technique, starting cold, allows the fat to melt gradually and results in crispier bacon. After about 2 minutes, increase the heat to medium-high and continue stirring for approximately 3 minutes until the pieces turn golden brown. Transfer the cooked bacon to paper towels to drain excess fat. The bacon will crisp up further as it cools, giving you perfect texture for topping your casserole.

2-Step 2: Prepare the Potatoes While the bacon cooks, peel your potatoes and cut them into 3 cm chunks. Keeping the pieces uniform in size ensures they cook evenly and finish at the same time. Place the cut potatoes in a large pot and cover them with water about 10 cm above the potato level. This generous water coverage allows for evaporation during boiling and ensures all pieces cook through. Add 1 tablespoon of cooking or kosher salt to the water. This step seasons the potatoes from within, creating a flavorful base for your casserole. Bring the pot to a boil over high heat, then reduce to a rapid simmer. Cook for about 15 minutes or until the potatoes are very soft and easily pierced with a fork.

3-Step 3: Drain and Dry the Potatoes This step is crucial for achieving fluffy mashed potatoes. Drain the cooked potatoes thoroughly in a colander, then return them to the warm pot. Let them sit for 1 minute, giving the pot an occasional shake. The residual heat from the pot evaporates remaining moisture from the potato surfaces. Excess water is the enemy of fluffy mashed potatoes, so don’t skip this drying step.

4-Step 4: Mash with Flavorful Additions Add the butter (75 g, cut into 1 cm cubes), 2/3 cup of milk, 1/2 cup of full fat sour cream or yogurt, and 1 teaspoon of salt to the pot with the dried potatoes. Use a potato masher to break everything down until smooth. Work quickly but gently to avoid overworking the starches. Important: Never use a food processor or electric beaters to mash potatoes. The high speed releases too much starch, resulting in a gluey, paste-like texture that no amount of butter can fix. Hand mashing gives you control over the texture. If you’re making this casserole ahead of time, add an additional 2/3 cup of milk at this stage. Refrigeration firms up mashed potatoes significantly, and that extra liquid keeps the mash creamy when it’s time to reheat.

5-Step 5: Prepare for Make-Ahead Storage (Optional) If you’re planning to bake the casserole later, now’s the time for storage. Let the mashed potatoes cool completely at room temperature, then transfer to your baking dish. Cover tightly with cling wrap and refrigerate for up to 3 days. When you’re ready to bake, remove the dish from the fridge 2 hours before reheating to take the chill off, which ensures even warming.

6-Step 6: Preheat and Assemble Preheat your oven to 200 degrees C (400 degrees F, or 180 degrees C fan forced). Spread the mashed potatoes evenly in a 2-liter or 2-quart baking dish, creating a smooth surface for the toppings. A smaller, deeper dish works better than a shallow one because it keeps the potatoes moist and allows the toppings to create a nice thick layer.

7-Step 7: Add Cheese and Bacon Topping Sprinkle 1 1/2 cups of tightly packed freshly shredded mozzarella cheese over the mashed potatoes, followed by 1 cup of tightly packed shredded Red Leicester, cheddar, or other flavored cheese. The mozzarella provides that amazing stretch when you scoop, while the aged cheese brings bold flavor and a beautiful orange color. Next, distribute the cooked bacon evenly across the top. The bacon pieces should be scattered rather than clumped, ensuring every serving gets some of that crispy, savory goodness. Potatoes offer surprising health benefits too, including potassium and vitamin C, making this comfort food more nutritious than many realize.

8-Step 8: Bake to Golden Perfection Cover the dish loosely with aluminum foil. If you just prepared the casserole and it’s still warm, bake covered for 20 minutes. If you’re reheating a make-ahead casserole that was refrigerated, bake covered for 35 minutes. The foil prevents the top from browning too quickly while allowing everything to heat through. Remove the foil and continue baking for an additional 10 minutes, or until the cheese is bubbly and developing golden spots. Keep an eye on it during these final minutes because the cheese can go from perfectly melted to overdone quickly.

9-Step 9: Garnish and Serve Remove the casserole from the oven and immediately sprinkle 1/4 cup of finely sliced green onion across the top. The residual heat slightly wilts the onions while keeping their fresh flavor and bright color. Serve immediately while the cheese is still melty and the bacon maintains its crunch. This casserole pairs wonderfully with roasted meats. If you’re planning a complete meal, consider serving it alongside oven baked chicken legs for a satisfying dinner that feeds a crowd.