I don't recommend freezing cooked shrimp toast. The bread will be soggy, and the shrimp mixture won't retain its crispiness when thawed. But...freezing uncooked shrimp toast is great. To freeze the toast, spread the triangles on a baking sheet and freeze until frozen. Drop them into a zip-top bag, squeeze out excess air, and freeze for up to 3 months. When ready to cook, let the toast defrost overnight in the fridge. Pat the toast to remove any surface moisture, then fry away as below.