Heat the heavy cream in a small pot on the stove over medium heat until hot but not boiling.
While the cream is heating, chop up the white chocolate into small bits. The smaller, the easier they will melt.
Put the chopped chocolate in a medium bowl. Add the hot cream.
Stir until the chocolate is melted.If needed, microwave at 50% power for 20 second intervals if the white chocolate is not completely melting.
Notes
If the ganache is too thick to use, first try warming it up a little. If this does not help, add a little more warmed cream and stir to combine.If your ganache is too thin and runny to use, you can simply let it sit for a little while at room temperature to thicken up as needed.