In a medium heavy-bottomed saucepan, whisk together all ingredients. Heat over medium heat, stirring occasionally, just until bubbles form around edges of pan. (Mixture should be gently bubbling; do not boil.) Simmer, stirring and scraping sides of pan frequently, until mixture is thickened and reduced to 1½ cups (about 448 grams), turns a cream color, coats the back of a spoon, and holds a trail when a finger is dragged through, 45 to 55 minutes. (Adjust heat as necessary to keep mixture at a simmer.)

Remove from heat; pour into a heatproof airtight container. Let stand, uncovered, until completely cool; cover and refrigerate for up to 1 week. Let come to room temperature before using.