For the strawberry habanero jam: In a 4-quart saucepan set over medium heat, add the sugar, orange zest and juice, and stir until the sugar dissolves. Turn the heat up to high and add the strawberries and habanero. Bring to a boil, stirring often, until the temperature reaches 200 degrees F on a candy thermometer. Once the jam has reached that temperature, remove it from the heat and allow it to cool slightly. Once cooled, you can serve immediately. Store any leftovers in an airtight container in the refrigerator for about a week.
For the custard: In a baking dish, whisk together the, milk, salt, sugar, nutmeg and eggs. Reserve.
For the sandwich build: Preheat a griddle over medium heat. Top a slice of Texas toast with a slice of cheese, one-quarter of the ham, a second piece of cheese and the second slice of toast. Dip the sandwiches into the custard, letting the excess drip off. Add some butter to the griddle and gently pan fry each sandwich until golden brown, 2 to 3 minutes each side. Remove from the griddle, dust with some powdered sugar, if using, and serve some strawberry habanero jam on the side.