Preheat your oven to 400°F (200°C). Arrange baguette slices on a baking sheet. Brush each side lightly with olive oil and sprinkle with a pinch of salt.

Bake 6–8 minutes, flipping halfway, until golden and crisp. Rub the warm slices lightly with the halved garlic for a hint of flavor. Set aside.

In a small saucepan, combine white wine vinegar, white wine (or water), shallot, and half the tarragon. Bring to a gentle simmer over medium heat and reduce until almost all liquid is gone—about 3–5 minutes. Strain and reserve the infused liquid. Let it cool slightly.

Tip: If you want a foolproof shortcut, skip the reduction and use 1 tbsp lemon juice + 2 tbsp white wine for a lighter shortcut béarnaise—still tasty and saves time.

In a heatproof bowl set over (but not touching) simmering water, whisk the egg yolks with the reduced liquid until pale and slightly thickened.

Slowly drizzle in the hot melted butter while whisking continually until the sauce is glossy and thick. Stir in the remaining tarragon, lemon juice, salt, and a pinch of cayenne. Keep warm over very low heat or in a thermos.

(If it gets too thick, whisk in a teaspoon of warm water.) Shortcut blender method: Place yolks and reduction in a blender. With blender running, slowly pour in hot butter through the lid opening until sauce emulsifies. Finish with tarragon and lemon.

Pat tenderloin medallions dry. Rub lightly with olive oil, salt, pepper, and thyme.

Grill over high heat (or use a hot grill pan) 2–3 minutes per side for medium-rare, depending on thickness. Aim for an internal temp of 125–130°F (it will rise as it rests). Rest the medallions 5 minutes before slicing thinly.

Place a small spoonful of béarnaise on each crostini. Top with a slice of grilled beef, a few microgreens, and an optional radish slice for crunch. Finish with a tiny sprinkle of chopped tarragon and a grind of black pepper.

Serve immediately while crostini are crisp and sauce is warm. These pair beautifully with a crisp white wine or a light red.