Whisk together vinegar, mustard, and honey, then slowly whisk in oil to create an emulsion. Set aside.
Core and chop pears into bite-sized pieces and slice chevre into 8 discs.
Combine spinach, arugula, pears, and cranberries in a large bowl and toss with half of the dressing. Divide lettuce mixture onto serving plates and top each with sliced medallion of goat cheese. Serve with remaining dressing on the side.