Bake until the custard is set, puffed up, and reaches an internal temperature in the center of 175 to 190ºF (79 to 88ºC), about 45 to 55 minutes. The less time you bake the casserole and the lower the internal temperature, the softer and more custard-like it will be. The longer you bake the casserole, and the higher the internal temperature, the more firm it will be.