01 - Place roasted hazelnuts into a food processor and blend for 4 to 5 minutes until smooth and creamy, scraping down sides as needed.
02 - Melt the chopped chocolate and softened butter together using a double boiler or microwave in 30-second intervals, stirring until fully smooth.
03 - Add the melted chocolate mixture, whole milk, powdered sugar, vanilla extract, and sea salt to the hazelnut butter. Blend until thoroughly combined and smooth.
04 - Pour the spread into a clean jar or airtight container and allow it to cool to room temperature; it will thicken as it cools.
05 - Store in the refrigerator for up to two weeks. Bring to room temperature before serving for optimal texture.