Beef Tenderloin Sliders with Horseradish Sauce - Jill's Kitchen

Ingredients

• 1 (2.5 to 3lb) beef tenderloin (preferably the center cut)
• 2 - 3 tsp kosher salt
• 1 - 2 tsp freshly ground black pepper
• 3 tbsp unsalted butter (melted)
• 1/2 cup mayonnaise (homemade or store bought)
• 1 tbsp prepared horseradish (or to taste)
• 2 tbsp whole or 2% milk
• freshly ground black pepper
• slider buns, any small bun will do
• spinach or arugula
• whole grain mustard