A monitoring and control system for monitoring the boil states of the contents of a cooking utensil located on a cooking surface of a cooktop, indicating the state to a user, and controlling the energy applied to the cooking surface, which may be a glass ceramic. The system includes at least one controllable heat source located below the lower surface of the cooktop so as to heat the cooktop and cooking utensil, at least one sensor located in proximity to the cooktop, which senses the temperature of at least one of the cooktop and the cooking utensil, at least one power indicative signal, and a signal processing device receiving a temperature signal from the sensor, and the power indicative signal. The signal issued by the sensor is representative of the temperature of either the cooktop, or the cooking utensil. In one embodiment the signal processing device detects a plateau in the sensor and power indicative signals, which is indicative of the boiling of the contents of the cooking utensil, or an increase in the rise of the sensor signal, which is indicative of a boil-dry condition in the cooking utensil. The signal processing device optionally is connected to a control device which automatically reduces the temperature of the heat source upon the occurrence of these conditions, or which provides an indication to the user that such conditions have occurred. Determining the boil states, such as boiling, boil-over and boil-dry for the contents of a cooking utensil on a glass ceramic cooktop is achieved by noting that a characteristic response exists in the signal generated by a temperature indicative sensor or the power indicative signal as the temperature of the contents of a cooking utensil on a glass ceramic cooktop approaches a boiling point.