Using the buttery, spread it on the outside of each slice of bread.
Spread Harissa on the opposite side, which will serve as an inner part of the sandwich.
On a slice, arrange the ingredients starting with tomatoes, spinach, basil, peppers, black pepper, then vegan cheese.
Cover the ingredients with the other slice, with the harissa side touching the cheese.
In the panini press, cook the sandwich on moderate heat for 4 minutes as you flip it halfway.
Remove the sandwich once the bread is brown and all the cheese gets to melt.