Instructions
Follow the steps and taste along the way.
Prepare the ingredients
Preheat the oven to 220 °C. Wash and dry the grapes. Peel the onion and cut it into thick wedges.
Roast the grapes
Spread the grapes and onion on a baking sheet. Drizzle with olive oil and sprinkle with thyme, salt, and black pepper. Roast for 20 to 24 minutes, until the grapes burst and the onion is lightly browned at the edges.
Simmer briefly
Transfer the contents of the baking sheet, including the juices, to a small saucepan. Add the water and balsamic vinegar, stir in the honey, and bring to a gentle simmer over low heat. Cook for 5 to 7 minutes to let the flavors come together.
Blend until smooth
Remove the saucepan from the heat and blend the mixture with an immersion blender until thick and glossy. It is fine if a few small pieces of grape skin remain.
Finish with butter and serve
Stir the butter into the warm sauce until melted and the sauce is glossy. Serve warm; it will thicken slightly as it cools.
