Cut potatoes in cubes and boil with salted water until al dente for 5 minutes. Drain and reserve.
While potatoes are cooking, bring a small pot over medium heat and stir butter with flour, cook for a minute to form a paste. Next, pour the milk and vegetable broth and whisk until the sauce becomes creamy and silky.
Add the sour cream, parsley, salt and cheese to the pot and stir to combine.
Fold the potatoes in the sauce gently and transfer to a prepared 6x9 baking dish.
Top with crushed cornflakes and more cheddar cheese and bake for 20 to 25 minutes until bubbly and cornflakes are golden brown.
Sprinkle extra parsley and serve.
Notes
Prep your potatoes perfectly. Peel for a smoother texture or leave the skins on for more texture. Cut into uniform cubes to ensure even cooking. This helps all pieces reach the perfect tenderness at the same time.
Boiling potatoes: It’s okay to cook potatoes to al dente as they will continue to cook in the oven when roasting. Don’t overcook them as they will become soggy.
Whisk continuously when adding the milk and broth to the roux to prevent lumps and ensure a smooth, creamy sauce.
Add sour cream and cheese to the sauce on a lower heat setting to avoid separating or curdling the dairy components.
When incorporating the potatoes into the sauce, fold them gently to maintain their shape and avoid breaking them down into a mash.
Keep an eye on the oven during the last few minutes of baking to prevent the cornflake topping from burning. Every oven is slightly different.