First, mix the milk, cheese, and cornstarch without heating, just to eliminate lumps by stirring a little.
Then add the butter, turn on the heat, and stir until it melts completely.
Continue stirring until the cheese reaches the desired point, i.e., when it easily detaches from the pan.
Then put it in a container (usually, we use glass dishes or ice cream boxes) and wait for it to cool.
Quick Strawberry Jam-Filled Muffins 
Ingredients:
