Preheat the oven to 180°C/350°F/gas mark 4.
In a large frying pan, lightly fry the kale in 1 tablespoon olive oil until some of its water evaporates and the kale becomes lightly crispy and with golden edges. Set this aside.
Cook the pasta in a large saucepan of salted boiling water for 2 minutes less than the packet suggests.
In another large saucepan, make a roux by melting the plant-based butter and adding the flour. Cook for 2-3 minutes to let the mixture thicken in the bottom of the pan. Next, ladle by ladle, slowly add the warmed oat milk, allowing each bit to be smoothly whisked into the roux before adding the next ladle.
Melt in the plant-based cheese and add the mustard and nutmeg. Add the cooked pasta to the sauce along with half a mug (150 ml) of pasta cooking water and the nutritional yeast.
Stir through the crispy kale and an extra tablespoon of olive oil for rich silkiness.
In a small food processor or bullet blender, combine the ingredients for the garlic breadcrumbs and blitz until you have a chunky crumb consistency.
Transfer the creamy cheesy pasta mixture to a large ovenproof dish and top evenly with the garlic breadcrumbs.
Bake for 20 minutes until the top is golden brown and bubbling. Leave to cool and set slightly before tucking in.