Heat oven to 240C/220C fan/gas 9. Put a large, ovenproof frying pan or two smaller pans in the oven to heat. In a food processor, whizz the eggs, milk, flour, 1 tbsp of the melted butter, 1 tbsp mustard and a pinch of salt. Leave to stand for 10 mins.
Meanwhile, cook the broccoli in boiling water for 2 mins, then drain and rinse in cold water. Remove the pan from the oven and pour in the remaining butter, then the batter. Cook for 20 mins until golden and puffed, adding the cheese, broccoli and ham for the final 2 mins of cooking. Stir 2 tsp mustard through the crème fraîche and serve alongside the pancake.