Spread the honey mustard over 2 of the tortillas. Layer with the pear slices and shredded gruyere, then top with the remaining tortillas.
Melt half of the butter in a large skillet. Add one quesadilla and cook until golden brown on the bottom. Flip and cook until the tortilla is golden and the cheese is melted. Repeat with the remaining butter and the other quesadilla. Slice into 16 wedges and serve.