Make the syrup. Simmer the vinegar in a small saucepan over medium-low heat until reduced to 1⁄4 cup. Remove the pan from heat and add the chocolate. Let the chocolate melt for 30 seconds, then gently stir the mixture with a small spatula until the chocolate has melted and the syrup is smooth. Add honey and salt and mix well.
Cover the pan to keep the sauce warm until you’re ready to serve the cauliflower.
Heat oven broiler. Arrange cauliflower in a single layer on a baking sheet. Brush both sides with olive oil and season with salt and pepper; broil, flipping once, until charred and crisp-tender, about 15 minutes. Drizzle half of the balsamic chocolate sauce onto a serving platter along with half the parsley and almonds. Top with charred cauliflower; drizzle the remaining sauce over top and garnish with the remaining toasted almonds and parsley. Serve.