when you add melted butter to the cold curdled milk mixture,
the butter will clump into little bits. this simulates the cold butter
bits that you want when cutting butter into flour and creates the
fluffy texture that is most desired in biscuits, especially in whole wheat. no need to pull out the food processor and have one more equipment to wash and you've still got fluffy whole wheat biscuits.
1. adjust oven rack to middle position and heat oven to 450 degrees.
2. mix the lemon into the milk. set aside and allow to curdle, about 5 minutes. i've found that it's easier to curdle milk with lemon than vinegar. milk mixture should be cold before mixing with butter.
3. whisk flour, baking powder, baking soda, sugar, and salt in large bowl.
4. add melted butter to milk mixture; stir until butter forms small clumps.
5. add milk mixture to dry ingredients and stir with wooden spoon until just incorporated and batter pulls away from sides of bowl forming a sticky ball. if batter feels too firm and dry bits are not gathering into a ball, sprinkle on more milk, about another tablespoon. be careful not to overmix, as that will give you a less fluffy biscuit.
6. spoon batter into approximately 1/4 cup portions and drop onto parchment-lined rimmed baking sheet, about 1 1/2 inches apart. bake until tops just begin to brown and become crisp, 12 to 14 minutes.
7. brush biscuit tops with melted butter, if you like. transfer to wire rack to cool.
you could, to save even more time, use buttermilk instead of the curdled milk mixture. i just like clabbering my milk, as it seems to have more of a tang and i'm too lazy to buy something when i've got a ready substitute at home.