Mix mayo, sour cream, and half the ranch seasoning in a small bowl. Chill.
In a large bowl, combine beef, Panko, and Worcestershire. Form into small balls (about golf-ball size).
Preheat griddle or cast iron over medium-high heat.
Melt butter with remaining ranch seasoning to create ranch butter.
Pour half the ranch butter on the griddle. Add beef balls, press firmly to flatten, and cook 1–2 minutes per side. Top with cheese (if using), cover, and melt.
Toast buns in remaining ranch butter for ~30 seconds per side.
Assemble sliders with sauce, patties, and toppings. Serve with extra sauce for dipping.