First make the pastry by putting the flours and salt in a food processor and quickly pulsing to combine. Cut the butter into small chunks and ad them to the flour. Pulse until you have a breadcrumb-like consistency. Add the cream, lemon juice and 1-2tablespoon of water to start and pulse so that it mixes and starts to come together. If it's not coming together after a couple pulses, add another tablespoon of water (the amount depends on your flour), pulse again, then add another if still needed. Once it comes together remove from the food processor, flatten into a disk and wrap in plastic wrap/cling film and refrigerate for around 30min. You can prepare it a day ahead as well.
When ready, preheat oven to 375F.
Peel, remove the ends and coarsely grate the parsnips. Peel and halve the onion then finely slice. Remove the stalks from the chard, trim the ends and thinly slice the stalks and shred the leaves. Keep them separately.
Warm the olive oil in a large skillet/frying pan and add the onion, stir and cook a minute or two. Then add the parsnip, stir and add the chard stalks. Cook all for around 5-10min, stirring now and then, until the vegetables have all softened. Add a little more oil if needed eg if the vegetables are sticking.
Meanwhile roll the pastry out fairly thin - around ⅛in/3mm thick - and put either on a lined cookie sheet or in a pie dish.
Add the chard leaves to the parsnip mixture once everything else has softened and stir in so they wilt, cook another minute.
Remove the vegetables from the heat once soft then add raisins, pine nuts and parmesan and mix through well. Pour the mixture into the middle of the pastry, flatten out slightly and fold over the pastry edges so that it holds the filling in.
Bake approx 40min until it's lightly browned over the top.