Your oven is not at the temperature it says
Most domestic ovens run ±15°C off the dial, and even after the preheat light goes out the walls and shelves are still coming up to temperature. Waiting another ten minutes after that light makes results far more repeatable.
An oven thermometer tells you your own oven's offset. That offset is the most common answer to "I followed the recipe and it is always underdone".
Convection wants 20°C less
A fan moves air, so heat transfers faster. Baking a conventional recipe on convection, drop the set temperature by 20°C or cut the time by 20%. Left as written, the outside colours before the inside is done.
Hob levels are read from the pan, not the dial
There is no standard for "medium". Judge by what the pan does instead.
- Low — garlic sizzles without colouring. Roughly 120–140°C.
- Medium — a water droplet spits and slowly disappears. Roughly 160–180°C.
- High — droplets bead and skate across the surface (the Leidenfrost effect). Above 200°C.
More on reading a pan in Heat control.
Smoke points
- Toasted sesame oil — 160–180°C. A finishing oil, not a cooking one.
- Butter — 150°C (the milk solids burn). Clarified, 250°C.
- Extra-virgin olive oil — 190–210°C. Fine for sautéing, wrong for deep frying.
- Canola, sunflower, grapeseed — 220–230°C. Suitable for frying.
- Refined avocado oil — 260°C, the highest of the common oils.