Whisk whole milk, heavy cream, granulated sugar, corn syrup, salt, and cornstarch together in a medium saucepan over medium heat. Stir constantly until the mixture reaches 170°F, about 8 to 10 minutes.

Strain the hot base through a fine-mesh strainer into a large bowl, stir in the vanilla extract, then press plastic wrap against the surface and refrigerate until below 40°F, at least 4 hours.

Pour the cold base into your ice cream maker and churn for 20 to 25 minutes until it reaches a thick, soft-serve consistency.

Serve immediately in cones or cups for soft serve, or transfer to a freezer-safe container and freeze for 2 hours for scoopable ice cream. Drizzle with chocolate sauce and serve.