For the sauce:

1. In a small bowl, mix 2 tablespoons of Dijon mustard, 2 tablespoons of ketchup, and 2 tablespoons of mayonnaise.

2. Add a splash of gherkin water to thin the sauce slightly, making it easier to spread.

3. Stir in 2 teaspoons of finely chopped onion.

4. Stir in 2 teaspoons of finely gherkins

5. Mix everything until smooth and creamy. Set aside for later use.

For the burgers:

6. Defrost the beef patties prior to cooking.

7.Toast the 2 brioche buns (cut side down) until golden and slightly crisp an set aside for later.

8. Season the 4 beef patties lightly with sea salt and freshly ground black pepper.

9. Heat a skillet or griddle over medium-high heat and cook the patties for about 2-3 minutes on each side. Add some chopped shallots and press them into the burger. 

For the serving:

10.Spread the prepared sauce generously on both sides of the toasted buns and layer the bottom bun with a cheese-topped beef patty, a few sliced baby gherkins, another cheese-topped beef patty. 

11.Place the top bun on and press gently.

Kali Orexi!