Using firm tofu instead of silken tofu is the first step in creating a thick vegan breakfast casserole that sets well. I also use some chickpea flour, which is a common ingredient in vegan egg recipes. If you don't have chickpea flour, you can use regular all-purpose flour or a gluten-free flour blend. And make sure you don't add too much liquid. The mixture should be pourable, but thick and creamy.