2.

Add cheese all at once and stir with a whisk to combine. Return pan to low heat and continue to whisk until mixture is homogenous and registers between 160 and 170°F on an instant read thermometer. Beat with the blade of an immersion blender directly in the pot until glossy and smoother. Alternatively, transfer to the bowl of a blender or food processor and blend, starting at the lowest speed and slowly increasing to the highest. Blend for 30 seconds, stopping to scrape down sides as necessary. If necessary, blend in two separate batches, pouring first half onto lined sheet tray before proceeding to second half (see step 3).