Preheat oven to 375 degrees F. Grease a 10-inch cast-iron skillet with butter, set aside.

In a large bowl, toss together the strawberries with the sugar, cornstarch, lemon zest, lemon juice, orange zest, and nutmeg until evenly combined. Pour the mixture into the prepared skillet. Shake into an even layer and set aside.

To make the biscuits, in a large bowl, combine the whole wheat and all purpose flour, sugar, baking powder, baking soda, and salt. In a measuring cup, whisk together the melted butter, buttermilk, heavy cream and vanilla extract. Make a well in the center of the dry ingredients, and pour in the wet. Stir gently with a rubber spatula until just combined and the dough comes together. The dough will be soft and sticky.

Using two spoons or a medium ice cream scoop (spring-loaded) and scoop out 8 biscuit mounds on top of the berries. Space them out evenly as they're rise and spread during baking. Brush the tops with the leftover liquid in the measuring cup and sprinkle with turbinado sugar.

Place the skillet over a baking sheet and bake until fruit is bubbling and the biscuits are golden brown, about 30 to 35 minutes. Remove from oven and allow to cool somewhat. Serve warm with ice cream or whipped cream. Cobbler is best the day of, but leftovers can be stored in fridge and rewarmed the next day or eaten cold.