Preheat the oven to 200°C (fan).
In a saucepan, boil the potatoes for 15-20 minutes. They are done when a knife easily pierces the centre, but they should not be falling apart.
Transfer the cooked potatoes to a baking tray. Gently smash them to crack open slightly by flattening with the base of a glass, mug, or pot. Be careful not to smash them too much but enough to ensure they open up. The aim is to release some of the starchy insides, which, when coated in a little oil and baked, turn wonderfully crispy.
Drizzle the oil mixture evenly over the potatoes, giving the tray a shake to coat them thoroughly. Sprinkle evenly with salt and pepper.
Roast in the preheated oven for 25-30 minutes, until golden and super crispy.
While the potatoes roast, mix together the sriracha mayo ingredients to make a great dip to accompany the crispy potatoes.
Serve the crispy smashed potatoes with the spicy sriracha mayo on the side.