Melt & Mix – Add the almond bark and peanuts to a slow cooker. Cover and cook on low for 2-3 hours, stirring occasionally until the chocolate is fully melted.
Cool Slightly – Turn off the slow cooker and let the chocolate mixture cool to room temperature (warm enough to stay liquid but not hot enough to melt the add-ins).
Add the Fun – Stir in the M&M’s and marshmallows gently until just combined.
Form the Clusters – Scoop 1-1 ½ tablespoon portions onto a parchment-lined surface.
Top & Set – Sprinkle extra M&M’s and sprinkles on top and allow the clusters to set before serving.