Been fiddling around with this.
Again, no measurments, sorry! Play with it! If the outcome depended on exact measurments, I'd write them down, I promise!
Cream cheese (1-2 oz?)
Cream (1/4 cup?)
pat of butter
Melt everything but cheese at low temp. Add in cheese and remove from heat, stir til melted.
Good on veggies, or on tortilla chips for nachos.
I used taco cheese with seasonings in it (NOT FG) and it turned out well!
In my experience, Monterey Jack alone ends up very stringy and clumpy in this type of thing.