Chop the butternut and leek into 3cm thick pieces, add to a roasting tray with the olive oil, chopped sage leaves, salt and pepper. Toss together then roast for 35 minutes.
Prep the gnocchi by adding to a pot of boiling salted water and boil for 2 minutes or until the gnocchi floats to the surface. Be sure not to overcook it.
Drain off the gnocchi leaving a ladleful of water in the pot (around 250ml) and put the cooked gnocchi in a bowl to the side.
Add the butter, dijon mustard, garlic powder and flour to the pot of gnocchi water and whisk together until smooth. Then add the gnocchi back in and stir in the sauce.
Once the leek and butternut is baked add the pot of gnocchi and sauce to the baking dish, stir together. Generously season with salt and pepper. Sprinkle over the sunflower seeds and dried parsley then return to the oven for around 10 minutes to finish baking.
Stir just before serving and garnish with more cracked black pepper. If you like, add a sprinkling of parmesan (dairy or vegan) to each bowl, to finish.
You can use dried gnocchi for this recipe. It will work slightly better as fresh gnocchi can go a little mushy when overcooked.