Cook the pasta according to the package directions. Drain when al dente and place in a large bowl.
Preheat the oven to 180°C/350°F/gas mark 4.
Heat 1 cup of the nondairy milk in a medium saucepan over medium heat.
In a cup, whisk the flour into the remaining ¼ cup of milk until dissolved.
Add it slowly to the heated milk, whisking as you go. Add the shredded vegan cheese and stir constantly until the cheese is dissolved and the sauce is bubbly, about 5 minutes. Pour over the pasta mixture and stir to combine.
If desired, place the pasta in a 9 by 13-inch casserole dish and cover with the bread crumbs. Bake, covered, for 20 minutes. Uncover and broil until browned on top, about 5 minutes.