Make the biscuits: (Can be made several hours ahead) In a large bowl, whisk together the flour, baking powder, sugar, salt and baking soda. Set aside.
In a small bowl, whisk together the buttermilk and melted and cooled butter, stirring until the butter forms small clumps.
Add the buttermilk mixture to the bowl with the dry ingredients and stir until just combined and the batter pulls away from the sides of the bowl. Using a 1/4 cup scoop or measuring cup, scoop out dollops of batter and drop onto a baking sheet, about 1 inch apart.
Bake in preheated oven until tops are golden and crisp, about 12-14 minutes. Remove from oven and brush tops with a bit of melted butter. Transfer to a cooling rack and cool 5 minutes before serving. (If making ahead, cool completely, then store in an airtight container at room temperature. Reheat in microwave briefly or pop into a 350F oven for 5 minutes or so.
For the peaches: Preheat a large skillet on the stove-top over medium high heat. Add the butter. When the butter starts to foam, add a few thyme leaves, if using and cook for one minute. Add the halved peaches, cut side down, and cook until bottom starts to colour. Once the peaches are coloured a bit, add the maple syrup and cook for about 30 second more. Add the lemon juice and a pinch of salt, then flip the peaches over. Let the syrup simmer until it is reduced by about half. Turn off the heat under the pan.
To serve: You can serve directly from the larger skillet you cooked the peaches in or transfer to smaller skillets or plates, topping with biscuits, thyme sprigs and a dollop of crème frâiche or yogurt, and spooning reduced syrup over-top. Garnish with fresh thyme sprigs and a bit of lemon zest. *I find it best to allow the peaches and syrup to cool to a bit before serving, for best flavour and to keep the creme fraiche or yogurt from melting too much.
*Make your own buttermilk by measuring out 1 cup of regular milk. Remove 1 Tablespoon of milk and add 1 Tbsp lemon juice to the milk. Stir, then return to the fridge to stand for 10-15 minutes.**Replace maple syrup with 2-3 Tbsp of brown sugar, or enough to make a nice, sweet glaze.