Hollandaise Sauce: Cut 2 tsp of the butter into small cubes; refrigerate until ready to use.
Meanwhile, in saucepan, melt remaining butter over medium heat; skim off foam. Reduce heat to low; keep warm.
In heatproof bowl, whisk egg yolks with cold water until pale and foamy, about 1 minute. Place bowl over saucepan of gently simmering water; whisk until mixture is thickened and foamy and holds a ribbon for at least 6 seconds when whisk is lifted, about 5 minutes.
Remove from heat; whisk in cubed butter, 1 cube at a time, until melted. Slowly whisk in melted butter. Whisk in lemon juice, hot pepper sauce and salt. If needed, gently whisk in up to 1 tbsp warm water, 1 tsp at a time, to reach desired consistency. Place bowl over saucepan of hot water (off heat)
to keep warm.
Eggs Benedict: In large saucepan or deep skillet, add enough water to come 2 to 3 inches up side; bring to simmer over medium-high heat. Stir in vinegar.
Crack 1 egg into small cup; gently slide into pan. Reduce heat to low; cook until white is set yet yolk is still soft, about 3 minutes. Using slotted spoon, transfer to paper towel–lined baking sheet to dry. Repeat with remaining eggs.
While eggs are cooking, in large skillet, cook bacon over medium-high heat, turning once, until lightly browned, about 5 minutes.
Assembly: Top each English muffin half with 2 strips of the bacon and 1 egg. Spoon hollandaise over top.
Tip from The Test Kitchen: To keep the poached eggs warm while you're cooking any remaining eggs, place them in a bowl of warm water. Transfer them to a paper towel–lined plate to dry briefly before serving.