Combine the wine, vinegar, mustard, shallots, tarragon, white pepper and cayenne in a small saucepan. Gently simmer over medium heat until the liquid evaporates, 3 to 5 minutes. Set aside to cool.

Melt the butter in a small saucepan over low heat until sizzling hot. Pour into a spouted measuring cup.

Place the cooled shallot mixture into a beaker or jar (about 1 pint or large enough to blend). Add the egg yolks and lemon juice. Using an immersion blender, blend to combine. Very slowly pour the melted butter down the side of the jar while blending to thoroughly combine; it will start to thicken and will be bubbly. Stir in the parsley and add salt if needed. Drizzle in the cognac and stir with a rubber spatula.

Season skirt with SPG or your favorite seasoning (but really, you don't want to over do it here. Let the Béarnaise do the talking on this one).

Heat grill to 550°, wipe down well with peanut oil.

Grill skirt 3 to 4 minutes per side. Transfer the steak to a heated platter and cover.

Let rest for 7-10 minutes. Slice the steak against the grain.

To plate, lay slices out, lightly drizzle warm sauce over meat, garish with parsley.