Rinse the asparagus under cool water and dry it well. Trim the tough ends from each spear. Patting the asparagus dry helps it char instead of steaming in the pan.

Place the asparagus in a bowl. Add olive oil, salt and black pepper. Toss gently until every spear gets a light coating. Keep the seasoning simple because the sauce brings plenty of flavor.

Place a large skillet or grill pan over medium-high heat. Let it become very hot before adding asparagus. A hot cooking surface creates those tasty dark marks and slightly crisp edges.

Add the asparagus in one layer. Cook for four to six minutes and turning often with tongs. The spears should become tender while developing several deep brown charred spots.

Add chopped shallot, vinegar and two tablespoons of water to a small saucepan. Simmer gently until the liquid reduces by about half. Remove it from the heat and let it cool slightly.

Melt the butter slowly in another saucepan. Keep the heat low and avoid browning it. Pour the melted butter into a small jug. This makes it easier to add gradually during sauce preparation.

Place the egg yolks in a heatproof bowl. Add the cooled vinegar mixture and lemon juice. Whisk until combined. Place the bowl over gently simmering water without letting the bowl touch the water.

Whisk the yolk mixture constantly while slowly adding melted butter. Continue until the sauce becomes thick, smooth and creamy. Keep the heat gentle because excessive heat can make the eggs scramble.

Remove the bowl from the heat. Stir in fresh tarragon, parsley, salt and black pepper. Taste the sauce and add more lemon juice if you prefer a brighter flavor.

Arrange the charred asparagus spears on a serving platter. Spoon warm béarnaise sauce over the top. Add a little extra tarragon if desired. Serve immediately while the asparagus remains warm and tender.