Finely chop the parsley, slice the chives, chop the thyme, mince the garlic, and zest and juice the lemon.
Melt the unsalted butter in a small saucepan over low heat until just melted and the foam subsides, 2–3 minutes.
Add the minced garlic and cook gently, stirring, until fragrant but not browned, 30–60 seconds.
Remove from heat and whisk in the Dijon mustard, Worcestershire sauce, lemon zest and juice, smoked paprika, crushed red pepper flakes, cayenne pepper, black pepper, and kosher salt until emulsified.
Stir in the parsley, chives, and thyme.
Taste and adjust salt or lemon to balance. Serve warm as a dipping sauce or drizzle for grilled steaks, chicken, seafood, or vegetables; or cool slightly and refrigerate until firm, 30–45 minutes, to use as a compound butter.