Combine the cream, sweetened condensed milk, and butter in a small sauce pan and place over low heat to warm.
Combine the sugar, water, and corn syrup in a heavy-bottomed, medium-sized sauce pan and stir gently. Place the pan over medium-high heat, and cook the mixture without stirring, lifting the pan and swirling the mixture periodically to ensure the sugar cooks evenly. Once the mixture begins to caramelize, and becomes a light amber color, about 8 to 10 minutes, you may remove it from the heat if the color is to your liking. if you like a darker caramel, with almost a burnt flavor, continue to cook the sugar until it reaches a dark amber color.
Remove the pot from the heat, carefully add the warm cream, condensed milk mixture, and stir. The caramel may seize up at this point, but once it is returned to the heat, it will smooth out again. Return the pan to the heat and stir the caramel until smooth. Attach a candy thermometer and cook the caramel until the thermometer reads about 220°F. Immediately add the vanilla, salt, and rice cereal to the caramel and stir to incorporate. Pour the caramel krispy mixture into the cooled, chocolate-coated crust until the caramel is almost flush with the edge of the crust (you will have about a cup of caramel left-over for eating straight from the fridge or drizzling on ice cream). Refrigerate (or freeze) the tart in order to set the caramel, about an hour.
Once the caramel has set-up, make the milk chocolate ganache. Combine the chocolate, cream and salt in a small microwave safe bowl and microwave on high for 15 to 30 second intervals, stirring after each interval, until melted and smooth. Pour the chocolate over the cool caramel, and spread the chocolate almost to the crust — I like to leave a border of caramel peaking out between the chocolate and the crust. Refrigerate for about an hour until the chocolate has set. sprinkle with sea salt and serve.