No. An immersion blender is a useful tool in the kitchen, but you can use a food processor or countertop blender to make blackberry vinaigrette if that's what you have on hand. Just like you would with a hand blender in a mason jar, start by pulsing your food processor or blender a few times to break down the fruit. Once the fruit is broken down, turn your machine to a medium-high mix setting and watch all the ingredients come together.