Preheat the oven to 180C/350F.
Place a large pan over medium-low heat. Pour in soy milk, season with salt, pepper, paprika and chili, add rosemary, garlic and thyme, bring to a boil.
1 cup soy milk, 1 rosemary sprig, 1 tablespoon paprika, 1 teaspoon chili flakes, 2 garlic cloves
Add chopped potatoes and broccoli florets into the pan of spiced milk, cover with a lid and let the vegetables steam for 15 minutes.
1 kg (2 pounds) potatoes, peeled and chopped, 400 g (14 oz) broccoli florets
Meanwhile, melt vegan butter, add butter, whisk and cook the flour for 1 minute. Pour vegetable stock into the flour mixture, add soy milk and nutritional yeast. Cook the sauce for 5 minutes or until thick and bubbly.
⅓ cup vegan butter, 3 tablespoon all-purpose flour, 1 cup vegetable stock, ½ cup soy milk, ½ cup nutritional yeast
Transfer vegetables (with leftover liquid but discard the herbs) into a 9x13 casserole dish, mix with the cheese sauce and top with vegan cheese. Cover the pan with foil and bake for 50 minutes. Remove the foil and let the cheese brown slightly.
½ cup vegan cheese