Prepare the biscuit topping by combing the flour, baking powder, salt, and cold butter. Use your hands or a pastry cutter to work in the butter to the flour mixture. It should be a bit gritty and have a sand-like consistency. Once reached, add in chives and stir in the milk. The dough will be a bit sticky and wet.
Melt the butter in an oven-safe skillet over medium heat. Add the diced onion and sauté until transparent and soft. Add the 3 tablespoons of flour, mix together, and cook for 1-2 minutes. Add in the 1 cup of milk and whisk together until no lumps remain. Whisk in the salt, sage, thyme, and pepper until combined. Allow the mixture to come to a simmer and whisk until it thickens.
Pour in the vegetable broth and bring to a simmer, whisking occasionally. Once thick and creamy, add in frozen vegetables. Simmer for 2-3 minutes, so it can cook warm thoroughly.
With your hands, drop large chunks of the dough over the top of the vegetable filling. I had about 8 evenly sized biscuits that topped my filling. The dough will be sticky to your hands, but that’s okay.
Once your filling is covered with the biscuits, place in the oven for 12-15 minutes or until the top of your biscuits are browned, so keep an eye on them.