Put all hollandaise sauce ingredients into a small powerful blender and blend until you get a smooth texture. You might have to add a little bit of extra warm water to get the desired consistency if it's too thick. Set aside until you're ready to warm it up right at the end.
Preheat oven to 375 degrees. Slice sweet potato into 1 inch thick slices and place on a baking sheet. Drizzle both sides with olive oil and season with salt and pepper. Roast until golden brown and slightly caramalized (about 30 minutes) flipping halfway through.
Either on the other side of your baking sheet as your sweet potato or a new one, trim asparagus stalks and then drizzle with olive oil and season with salt and pepper and roast until slightly softened and browned. These will be done sooner than your sweet potato (around 15-20 minutes) so just keep an eye on them!
While the sweet potato and asparagus is roasting, fill a medium sized pot halfway with water. Make sure to put enough water to fully submerge your eggy. Heat water over medium-high but don’t let it boil! You just want to get the water very hot and when you start to see bubbles come-up, control the temperature by dropping it down to medium heat.
Put a splash or two of vinegar in your water. This helps your egg firm up faster so the egg whites don’t disperse in the water.
Crack your egg into a small dish, make a whirlpool in the water with a spoon and slide your egg into the middle of the wirlpool. Repeat with the remaining eggs all in the same pot. Keep an eye on it, but it usually takes about 3-4 minutes for a perfectly cooked poached egg. Nudge it a little with your spoon to make sure the whites are fully cooked, but you want a wobbly egg, not a hocky puck. Remove with a slotted spoon and drain on a paper towel.
When you're ready to assemble, place your cashew hollandaise in a small pot and heat over low until warm. If it starts getting to thick, you can add in splashes of hot water and stir until you get the right consistency.
To assemble, place sweet potato toast on a plate and top with asparagus and poached egg. Pour a little cashew hollandaise on top and garnish with microgreens or herbs!