For the biscuits:

Heat the oven to 425°F and arrange a rack in the middle.

Line a baking sheet with parchment paper and set it aside.

Whisk the flour, baking powder, salt, and baking soda together in a large bowl to aerate and combine.

Add the butter pieces and toss to just coat them in the flour mixture. Place the bowl in the freezer for 10 minutes.

Using a pastry blender or 2 knives, and working quickly so as not to soften the butter, cut the butter into the dry ingredients until it’s in pea-size pieces.

Drizzle in the milk, add the chives and lemon zest, and stir with a wooden spoon just until a moist, shaggy dough comes together.

Pat the dough into a disk and divide it into 6 equal portions (about 1/2 cup each).

Pat each portion into a 2-1/2-inch-wide disk and place them on the prepared baking sheet, spacing them about 2 inches apart.

Bake until the biscuits have risen and are golden brown on top, about 15 to 16 minutes.

Transfer to a wire rack to cool while you make the hollandaise sauce and poach the eggs.

For the hollandaise sauce:

Fill a large saucepan a quarter of the way full with water and bring it to a simmer over high heat.

Remove from the heat and set aside.

Place the egg yolks and lemon juice in a blender and blend on medium speed until the mixture lightens in color, about 30 seconds.

Reduce the blender speed to low, remove the small cap from the lid (the pour lid), and slowly drizzle in all of the melted butter.

Turn off the blender, add the measured salt and pepper, and pulse to combine.

To keep the hollandaise sauce warm, place the blender pitcher directly in the reserved hot water while you poach the eggs.

For the poached eggs:

Bring the measured water to a simmer in a medium pot over high heat (the water should be at least 2 inches deep). Reduce the heat to low to keep the water at a bare simmer. Stir in the vinegar.

Break 1 egg into a small cup or ramekin. Gently slide the egg into the simmering water. Repeat with the remaining 5 eggs, making sure to evenly space them in the water.

Cook until the whites are just set, about 3 minutes.

Lift the eggs out of the water with a slotted spoon. Place in a bowl of warm water to keep warm.

To assemble:

Cut each cooled biscuit in half and place the bottom halves on serving plates.

Place the crabmeat in a medium frying pan over medium heat and cook, stirring occasionally, until warmed through, about 6 to 8 minutes.

Divide the crab among the bottom biscuit halves.

Using a slotted spoon, remove the eggs from the warm water. Blot any excess water from the underside of the spoon with a paper towel or kitchen towel and slide the eggs onto the crab.

Top the eggs with the desired amount of hollandaise sauce (you may have some left over to serve on the side).

Prop the biscuit tops against the sides of the Benedicts, sprinkle with chives, and serve immediately.