Cut goat cheese into 12 (1/4-inch-thick) rounds; shape into tidy disks. Freeze until firm, 10 to 15 minutes. Combine lemon juice and chopped radishes in a bowl.  Heat canola oil in a large skillet on medium-high heat. Place panko in a shallow bowl. Place egg in a second bowl. Dip chilled cheese in egg, letting excess drip off, and then in panko, pressing gently to help it adhere. Fry, in batches, turning once, until golden brown, 45 seconds to 1 minute. Transfer to a paper towel-lined plate. Add olive oil, honey, and mustard to radish mixture; whisk to combine. Toss together spinach, mint, blueberries, sliced radishes, and vinaigrette in a bowl. Serve topped with crispy goat cheese.