Preheat your oven to 200 degrees C (fan forced) or 220 degrees C (for an older, slower oven). Whisk the eggs and sugar in a Pyrex bowl, then mix in the milk, flour and vanilla extract. Whisk until smooth. Gently fold in the raspberries.

Meanwhile, heat a 9-10 inch cast iron skillet and melt the butter quickly, allowing it to turn 'nut brown' (taking care not to burn it), then pour in the pancake batter. Sprinkle the hazelnuts over the top.

Now, pop the skillet into the hot oven and bake the pancake for 15-20 minutes until the edges curl and it has puffed up and is golden brown.

Remove from the oven onto a trivet. Dust with icing sugar and serve. Note: the pancake will deflate quickly, so best to serve it immediately. However, it is also delicious when cool.