Add milk, cream, and sugar to a large saucepan over medium heat. Heat and stir until the sugar is completely dissolved.
½ cup milk, ½ cup cream, ½ cup granulated sugar
Add your cornstarch and whisk until there are no visible lumps. Continue to heat, stirring frequently, until your sauce thickens (cornstarch will only start to thicken sauce once it reaches 295°F so be patient!).
1 tablespoon cornstarch
Once your sauce is nice and thick (think glue), remove from heat and transfer to a bowl. See pro tips for more info on thickening!
For a thinner sauce, heat, and stir until the consistency resembles glue before moving on to step 4. For a thicker sauce, continue to heat until the sauce resembles pancake batter. Keep in mind we will be loosening the sauce after heating by adding Brandy, so at this stage, you want your sauce even thicker than you want the final outcome.