This sauce is an essentially crème anglaise enriched with almond butter and almond extract. Crème anglaise is the classic French vanilla sweet-cream sauce that is the base for vanilla ice cream and crème brûlée.
You must use whole milk rather than lower fat varieties or the sauce won’t set. Almond butter is available in most supermarkets as an alternative to peanut butter. Make sure you get an extra smooth variety. Vanilla bean really puts this sauce into the realm of the spectacular. Cardamom and almond are a pairing common in the Middle East, and a flavor that was very popular in Europe during the Medieval period. The cardamom adds an almost minty aroma and flavor to the sauce that makes it an ideal pairing with fruit-based desserts like an apple or pear strudel.