Peppermint Hot Fudge Sauce

Ingredients

• 2/3 cup heavy or whipping cream
• 1/2 cup light corn syrup or golden syrup
• 1/3 cup packed dark brown sugar
• 1/4 cup unsweetened cocoa powder, ideally dutch-processed
• heaping 1/4 teaspoon fine sea salt or level 1/4 teaspoon table salt
• 6 ounces bittersweet chocolate, chopped (or, about 1 cup bittersweet chocolate chips), divided
• 2 tablespoons unsalted butter
• 1/4 teaspoon peppermint extract, or to taste
• crushed candy canes, for serving (optional)