-
Heat 1/4 cup oil with 1 cup basil in medium saucepan over medium heat until basil turns bright green and small bubbles appear, 2 to 3 minutes.
-
Turn off heat and steep 5 minutes.
-
Process shallot, garlic, vinegar, water, salt, pepper, and mustard in blender until garlic and shallot are finely chopped, about 15 seconds.
-
With blender running, slowly add remaining oil and steeped basil oil and continue to process until dressing is smooth and emulsified, about 15 seconds.
-
Pack remaining basil into blender and process until dressing is smooth, about 15 seconds.
-
Dressing can be refrigerated in airtight container for up to 3 days.