This sauce becomes firm and chewy when served over ice cream.
Mix in a large heavy saucepan:
Whisk in until well blended:
Bring to a simmer over medium-high heat. Remove from the heat and whisk in:
Return to medium-high heat and boil, whisking frequently, until the bubbles become small and the syrup is thick and sticky (about 225°F on a candy thermometer), 5 to 8 minutes. Remove from the heat and add:
Whisk until smooth. Serve at once, or let cool. Cover and refrigerate for up to 2 weeks. Reheat in a heavy saucepan over low heat.