1 cup oil (sunflower oil works great in this; for the most amazing BLT ever, make it with melted (but not hot) bacon fat!)
1/2 tsp salt
1/2 tsp dry mustard
1/2 tsp honey
1 Tbsp distilled vinegar
2 tsp lemon juice
If you have a stick blender, you simply add all the ingredients to a pint-size jar, rest the stick blender on the bottom of the jar, hit the "on" switch, and slowly raise the shaft to the top of the mixture. It should take about 5 seconds.
If you're using a conventional blender, you need to put all ingredients but the oil into the blender, mix lightly, then drizzle oil into the blender jar as slowly as you can. This will take much longer, but the final result will be the same.