01 - Preheat oven to 350°F. Line a baking tray with parchment paper.
02 - In a small bowl, whisk together Dijon mustard, whole-grain mustard, honey, lemon juice, salt, and black pepper until well combined.
03 - Carefully slice each mini slider bun horizontally. Place the bottom halves onto the prepared baking tray.
04 - Layer each bun base with a portion of the thinly sliced halal corned beef. If opting to use cheese, place a slice of halal Swiss cheese on top of the corned beef.
05 - Place two dill pickle slices onto each slider assembly. Spoon a small amount of the prepared mustard sauce over the meat and pickles.
06 - Position the top halves of the slider buns onto each assembled slider. Using a pastry brush, evenly coat the tops of the buns with the melted unsalted butter.
07 - Transfer the baking tray to the preheated oven and bake for 7 to 10 minutes, or until the slider buns are lightly golden and the cheese is thoroughly melted and bubbly.
08 - Remove the sliders from the oven. If desired, sprinkle finely chopped fresh parsley over the tops for garnish. Serve warm, offering any remaining mustard sauce on the side for dipping.