Prepare the crust: Mix the melted butter and biscuit crumbs and press the mixture lightly into a baking dish. Place it in the refrigerator.
Prepare the filling: Place the butternut and onion in the roasting tin and drizzle olive oil on top. Season to taste with salt and black pepper and sprinkle some dried sage on top.
Oven roast until cooked and soft. Remove from the oven and leave to cool down a little.
Place the cooked butternut and onion mixture into the prepared crust. Combine the cream cheese, sour cream and eggs and pour this over the ingredients in the crust.
Reduce the heat of the oven to 180C and bake for approximately 1 hour until set and golden brown. Serve the Butternut bake with a fresh salad of choice.