1 Squeeze juice from oranges. Bring 175 ml (approximately 3/4 cup) of juice to a boil in a small pot over medium heat until the liquid has reduced to about 1/3.
2 Stir in mustard and balsamic vinegar and season with salt and pepper.
3 While whisking, slowly drizzle in olive oil until combined.
4 Alternately, combine all ingredients in a jar, screw on the lid and shake vigorously to combine.