In a food processor, blend together the fresh raspberries, white wine vinegar, dijon mustard, and shallot. Pulse in the olive oil until just combined.
Transfer the dressing to a fine mesh sieve over a bowl or jar. Use a spoon to push the vinaigrette through the holes, leaving behind the seeds. Transfer the vinaigrette to an airtight container, season with salt and pepper and refrigerate until ready to use.
Olive oil becomes bitter when blended at high speeds, like with a food processor. Try to add the olive oil in gentle pulses rather than straight blending so that you can see exactly when it is combined and stop before the polyphenols release and make the vinaigrette bitter.
Want to make the flavor of this vinaigrette even more unique? Substitute a tablespoon of the oil with a seed or nut oil instead. Try using walnut oil, pumpkin seed oil, or hazelnut oil. These oils shine in a cold dish like salad and take your vinaigrette to the next level.
If you need to use frozenraspberries it is better to measure the berries while still frozen. However, if they're stuck together at all this may be hard to do. If measuring thawed, spoon the raspberries into the measuring cup being really careful not to squish and compact them.
Another alternative to fresh berries is raspberry jam. This creates a much sweeter vinaigrette because most of the tangy bite that raspberries have is already overbalance with sugar for preserving. At the very end, thin out the dressing with water or fruit juice to get it to the right consistency.