In a high-speed blender, add egg yolks, lemon, mustard, and salt and blend until smooth. Add butter to a small saucepan and melt over low heat. You want the butter to be very warm/hot when you pour it into the blender.
With the motor running, slowly pour in the hot butter (it may splatter a bit, so use your hand as a guard). Blend on high until smooth and emulsified. Now your sauce is ready! Transfer it to a heat-safe bowl. Don’t put it in the fridge, we want it to stay warm otherwise it will solidify. If it sits too long and is too thick, you can microwave on low power for 10 seconds.
In a large non-stick skillet over medium-high heat, cook the breakfast sausage in a little bit of oil until cooked through and browned, about 5 minutes, breaking up into small chunks if using raw. Transfer to a paper towel lined plate or bowl. Pour off any excess oil, but leave a little bit in the pan to cook the eggs.
Add the eggs to the skillet over medium heat and scramble them up. Transfer to a plate and top with cheese immediately so it can melt onto the eggs (cover with a towel or foil to keep warm).
In that same skillet, warm your tortillas (or do this in the oven). Now assemble! Fill each tortilla with sausage and cheesy eggs. Drizzle the hollandaise sauce over top and sprinkle generously with herbs.