Spread the vegan butter on the two pieces of bread.
Place one piece of bread in a frying pan, butter side down. Turn the heat to medium low.
Place the two pieces of vegan cheese (and the pesto if using) on the bread. Place the other slice of bread on top, butter side up.
Place a lid on the pan to seal in the heat and help the cheese to melt.
Check the grilled cheese after a few minutes. If it is golden brown on the bottom, flip it and continue to cook on the other side. The second side will probably not take as long to brown. Reduce heat if needed.
Slice the grilled cheese in half and serve with pickles if desired.
Notes
This sandwich is best eaten right away. You could store it in the refrigerator, but the quality won't be great.