- In a large saucepan over medium-high heat, bring the 2 syrups to a boil and cook until a candy thermometer reaches 111°C (232°F), about 15 minutes.
- Place the saucepan in a basin of cold water. Let cool, without stirring, until the thermometer reads 20°C (70°F), 20 to 30 minutes.
- Remove the saucepan from the water. Using an electric mixer, beat until creamy, 2 to 3 minutes. Cover and refrigerate for 2 hours. Store refrigerated for up to 3 weeks.