Preheat the oven to 450F. Place a regular muffin pan or popover pan on the middle rack to heat while you make the batter.

Prepare the popover batter. In a large bowl, whisk together the milk, eggs, sourdough discard, and melted butter until combined and smooth.

Sift in the flour and salt, and whisk until the large lumps are gone, being CAREFUL not to over-mix. A few small lumps are fine.

Transfer the batter to a large measuring cup or glass to make it easier to pour.

Cut up 3 tbsp of butter into small pieces. Carefully remove the hot pan from the oven, and place a small piece of butter in each well; the butter will melt. If needed, place the pan back into the oven for 1 min, until the butter is melted.

Working quickly, pour and divide the popover batter evenly among each muffin well, filling each ¾ of the way.

Quickly place the pan into the oven and shut the door.

Bake at 450F for 20 mins. Make sure NOT to open the oven door while baking, this will let steam out of the oven and cause the popovers to fall. After 20 mins, reduce the heat to 350F and continue to bake for another 10-15 mins, until golden and puffy.

While the popovers are baking, make the whipped honey cinnamon butter. Place the butter in a medium bowl. Whisk to beat using a hand mixer.

Then, add in the honey, cinnamon, and vanilla, and whisk or beat until well combined and fluffy.

Once the popovers are done baking, remove from the pan and immediately serve with the whipped honey cinnamon butter and a sprinkle of flaky sea salt, if desired.