Whole-Wheat Popovers

2 tablespoons plus 6 teaspoons salted butter, plus more, at room temperature, for serving
1½ cups whole milk, at room temperature
3 large eggs, at room temperature
2 teaspoons vanilla extract
1 cup whole-wheat pastry flour
½ cup all-purpose flour
1 teaspoon fine pink Himalayan salt
Maple syrup for serving
1. Preheat the oven to 450°F with a rack positioned in the lower third of the oven.
2. In a small skillet over medium heat or using the microwave, melt 2 tablespoons of the butter. In a medium bowl, vigorously whisk together the milk, eggs and extract until frothy, about 1 minute. Add the melted butter, both flours and the salt, and whisk to combine. It's okay if there are some small lumps
3. Place 1 teaspoon of the remaining butter in each cup of a 6-cup standard popover pan. (Alternatively, you can use a 12-cup muffin tin to make mini popovers, using ½ teaspoon butter per cup.) Transfer the pan to the oven for 2 to 3 minutes to melt the butter and heat the pan.
4. Carefully remove the popover pan from the oven and tilt it in a circular motion to coat the cups with butter. Divide the batter evenly among popover cups, filling each three-quarters of the way.
5. Bake for 15 minutes. Do not open the oven- your popovers might deflate. Then reduce the oven temperature to 350°F and bake until popovers are puffed, golden, and crisp, 10 to15 minutes more.
6. To serve, split the warm popovers in half and spread them with butter and the maple syrup. Enjoy!