Place butter, corn syrup, brown sugar, cocoa powder, and chocolate in a medium saucepan. Cook over medium-low heat until chocolate is fully melted, stirring constantly.
Stir in evaporated milk, bring to a boil, and continue to cook until sauce thickens, about 5 to 10 minutes, stirring occasionally.
Remove from heat and add in vanilla, chili powder, and orange extract; stir to combine. Season with salt to taste.
Let sauce cool until warm, then serve over ice cream or store in an airtight container in the refrigerator for up to a week, reheating before use.
