Heat the milk in the microwave for about 30 seconds until hot and begins to boil.
Pour ingredients into the blender. Pour the milk, egg yolks, miso, sugar, and pepper into the blender and blend on low for 3 minutes, until the mixture is smooth, velvety, and foamy. The mixture should almost double in size.
Add the lemon juice and blend until evenly mixed. Set aside.
Brown the butter. In a small nonstick saucepan, cook the butter over medium heat for about 5-6 minutes, swirling the pot frequently. You’ll notice that the sizzling sound subsides and the butter starts to foam and smell nutty. Stop cooking when the butter is brown and fragrant.
Emulsify the butter with the other ingredients. While the blender is on low, slowly drizzle in the hot butter into the blender using a spoon. You can increase the speed of the butter halfway through but be sure to blend the butter really slowly in the beginning. This should take about 5 minutes. When all the butter is in and blended, the sauce will thicken and shine.
If the sauce begins to separate mix in table spoon of warm milk.
Serve with poached eggs, bacon, spinach on an english muffin. Top with toasted sesame seeds and green onions for the ultimate brunch!