Step 1: Preheat your oven to 425°F (220°C).
Step 2: Place the popover pan in the oven for about 5 minutes to heat it up.
Step 3: In a small saucepan, melt 2 tablespoons and 6 teaspoons of butter over medium heat. Set aside to cool slightly.
Step 4: In a mixing bowl, whisk together the whole milk, eggs, and melted butter. Gradually add in the flour, kosher salt, and optional black pepper until just combined.
Step 5: Remove rosemary leaves, chop finely, and fold into the batter.
Step 6: Pour the batter into the hot popover pan, filling each well about ¾ full.
Step 7: Bake for 20-25 minutes until puffed and golden brown. Do not open the oven door during baking.
Step 8: While baking, prepare the honey butter by mixing room temperature butter, honey, and flaky sea salt until smooth.
Step 9: Serve warm with honey butter on the side.