Set a dry frying pan with the pecans over a medium heat. Sprinkle over the sugar, season and toss well to coat. Cook for 3-4 minutes, shaking often, until the nuts are toasted and the sugar caramelised. Tip onto a plate and leave to cool.
Cook the romanesco florets in boiling salted water for 2 minutes. Drain well, refresh in a bowl of ice-cold water, then drain again.
For the dressing, beat together 50g blue cheese, the milk and olive oil until combined. Stir in the lemon juice.
Arrange the romanesco florets and apple slices on a platter. Scatter over the parsley, reserved cheese, pecans and lemon zest. Drizzle with the dressing and serve extra on the side.