Preheat the oven to 400°F.
Place an 8-inch springform pan on a half sheet tray.
Carefully slice each pretzel bite about 70% of the way through, similar to a small hot dog bun. Do not cut completely through the pretzel bite.
Spread approximately 1 tsp chive cream cheese inside each sliced pretzel bite.
In a medium bowl, combine the melted butter, finely grated Parmigiano cheese, whole grain mustard, Dijon mustard, and finely minced garlic.
Stir until the mixture is evenly blended.
Arrange one layer of the stuffed pretzel bites in the prepared springform pan.
Brush the first layer with half of the garlic mustard butter mixture.
Sprinkle half of the grated mozzarella cheese evenly over the first layer.
Arrange the remaining stuffed pretzel bites over the first layer.
Brush the remaining garlic mustard butter mixture over the top.
Sprinkle the remaining mozzarella cheese evenly over the pretzel bites.
Bake for 12 to 15 minutes, or until the cheese is melted, bubbly, and lightly golden.
Remove the pan from the oven.
Allow the pretzel bites to cool for several minutes before serving.
Serve warm with cheese sauce or the preferred dipping sauce.