In a bowl, combine hash browns, egg, green onions, cheddar cheese and salt. Mix thoroughly to combine.
Spoon mixture into greased waffle iron and press until golden brown and crisp, about 10-15 minutes. Cut the waffle into four portions.
Select a cup or glass cylinder that just fits the head of immersion (stick) blender. Combine egg yolks and water.
In a small pot, over medium heat, melt butter until simmering and no longer foaming, about 1-2 minutes.
Transfer to measuring glass with pouring spout. Insert immersion blender into bottom cup with egg yolks and start blending. With the blender running, slowly pour hot butter in until completely smooth and creamy.
Stir in lemon juice, salt and pepper to taste. Thin with additional water, if needed. Set aside or keep warm in 2 inches of warm tap water.
Slice sausages lengthwise almost all the way through. In a greased non-stick skillet over medium heat, fry sausages, flipping once, until browned and crisp. Move to a paper towel-lined plate to drain.
Wipe pan clean, grease and cook eggs, flipping once until cooked but soft in the middle, about 2-3 minutes.
To serve, top each waffle piece with sausage, egg and hollandaise sauce. Garnish with mixed microgreens.