1. Preheat the oven to 375ºF (190ºC).
2. Hull the strawberries and cut them in quarters. In a wide shallow baking dish with high sides (one that will fit all the berries in a single layer, with space between them), toss the berries with the golden syrup, balsamic vinegar, and black pepper.
3. Spread the berries across the bottom of the baking dish and roast on an upper rack of the oven, stirring once or twice during roasting, until they are well-cooked and the juices have thickened substantially, about 30 to 40 minutes. Remove from the oven and scrape into a bowl. Once cool, take a pair of scissors and snip the cooked berries into smaller pieces, directly in the bowl.
(The berries can be prepared up to three days ahead, and refrigerated.)
4. To make the ice cream custard, heat the milk and sugar in a saucepan.
5. While the milk is warming, make an ice bath by placing a 2-quart (2l) bowl in a larger bowl partially filled with ice and water. Set a strainer over the top of the smaller bowl and pour the cream into the bowl.
6. In a separate bowl, whisk together the egg yolks and miso. Gradually pour some of the warm milk into the yolks, whisking constantly as you pour. Scrape the warmed yolks with miso and milk back into the saucepan.
7. Cook over low heat, stirring constantly and scraping the bottom with a heat-resistant spatula, until the custard thickens enough to coat the spatula. Strain the custard into the heavy cream. Stir over the ice until cool. Add the vanilla extract and refrigerate to chill thoroughly, preferably overnight.
8. To finish the ice cream, mix the roasted strawberries with the miso ice cream custard, then churn in your ice cream maker according to the manufacturer’s instructions.