You can make meringue in a food processor as long as your food processor has a whisk attachment.
If your food processor has a whisk attachment you can make the meringue in the food processor by turning the food processor on for a few minutes.
A countertop blender can be used to make Meringue with.
If you do use a countertop blender to make Meringue you want to use the slow setting on the blender so it does not blend or mix it too fast.
When making Meringue it's best to blend it with a hand mixer or hand whisk but a countertop blender can work to make Meringue when done right.
You can make stiff peaks with a blender.
To make stiff peaks with a blender you put the blender setting on gentle speed and slow blend it until it's at stiff peaks.
However for best results it's best to beat to stiff peaks by hand mixing it but the electric blender will work to beat to stiff peaks as long as you don't blend it too long.
When making meringue and beating it to stiff beaks it takes around 5 minutes to beat the meringue to stiff peaks.
It can take awhile for the sugar to dissolve and for the meringue to reach stiff peaks.
But it should only take around 5 minutes of beating the meringue before it reaches stiff peaks.
If the sugar in the meringue has not dissolved fully then you still need to beat it some more until the sugar dissolves and so that it doesn't taste gritty.
Once the sugar has dissolved and it doesn't taste gritty anymore then you've beaten it to stiff peaks and it's ready.
But usually 5 minutes is enough to beat to stiff peaks which has been my experience.