Lemony Strawberry-Rhubarb Cobbler

Soften 1 tablespoon of butter, and use it to grease the entire inside of the slow cooker crock. Place the lemon peel and peppercorns in a cheesecloth bag and tie with kitchen string. Add this bag plus the remaining butter (cut into eight pieces) and other filling ingredients to the slow cooker, and gently mix with a wooden spoon. Cover and cook on low until the fruit is softened, about 4 hours (there will still be some liquid).
About 45 minutes before the fruit is finished, heat the oven to 400°F, and line a baking or cookie sheet with parchment paper. Whisk together the dry drop biscuit ingredients (with the exception of 1 teaspoon of the sugar) and the lemon zest in a medium-size bowl. Gently stir in 1 cup plus 1 tablespoon of the heavy cream. Use your hands to form a soft, relatively smooth dough, taking care not to overmix. Divide the dough into six balls and place on the lined baking sheet. Flatten each one to the thickness of about 1/2 inch. Then pour the remaining tablespoon of cream into a small bowl and put the remaining 1 teaspoon of sugar into another small bowl. Using a pastry brush, brush each biscuit with the cream, then sprinkle with the sugar. Bake until slightly golden and cooked through (when tested with a fork, it should come out clean), 20 to 25 minutes. Set the biscuits aside.
Once the fruit is cooked through, carefully remove the sachet. Place a large strainer over a medium to large, heavy saucepan, then—using oven mitts—pour the fruit mixture into the strainer. Set the fruit (in the strainer) aside. Boil the liquid over high heat until reduced to 3 to 31/2 cups, about 20 minutes. Add the fruit to the pot with the thickened liquid, and mix.
Use a ladle to divide the fruit mixture among six bowls; top each portion with a biscuit and a scoop of vanilla ice cream, if desired.