Make the muffin batter! It will need to rest at room temp for 30 minutes before baking. First, in a large bowl, whisk together the eggs, white sugar, oil, sour cream, milk, and vanilla extract until thicker and smooth. Place your salted butter and the 4oz of dark chocolate (chopped into chunks) in a microwave safe bowl and melt for 45-90 seconds, stirring after 45 seconds, until the butter and chocolate have melted together. Slowly pour in this melted mixture into the wet ingredients and whisk until smooth. Add in the gluten free 1-1 flour, xanthan gum if your mix does not already contain it, regular and dutched cocoa powders, baking powder, and salt and stir until just combined (do not overmix). Finally, fold in the chopped (peeled) pears.
Then place your six 4-inch cake pans on a cookie sheet and grease each pan with cooking spray or room temp butter, then spoon batter into each one evenly (they should be about 3/4-5/6 full). Then let the batter sit either on the counter for at least 30 minutes before baking (you can let it rest in the fridge for longer if you want).
Once the batter has rested preheat the oven to 425° Fahrenheit. Bake for 5 minutes and then turn down the temperature to 350° (without opening the oven door!! Keep it closed) and continue 25-30 minutes until the tops spring back with touched (do NOT open the oven while baking or the muffins will not rise fully, only open the oven a tiny bit to check if done). Let cool nearly-completely before turning out.
While the muffins are cooling, make the glaze! In a medium bowl, stir together all of the glaze ingredients, starting with 1 tbsp of milk and adding the rest of the milk as needed (you may not need all of it), until fully combined and very smooth (this may take some working). Check the consistency of the glaze: you're looking for a glaze that can pour over the muffins, but doesn't flow too quickly or it will simply run off and not hold on top of the muffins, when in doubt, thicker is better. Add more powdered sugar if it seems too thin/runny. Taste as you go! Add the salt last, and taste to be sure it's the right amount - it should enhance the chocolate flavor.
Then use a spoon or small pitcher to pour the glaze over the muffins, and serve! You can let the glazed muffins sit at room temp for 30-45 minutes for the glaze to harden, then put into zip-top bags and keep in the fridge or freezer for up to a week. Best-served slightly warm, so pop them in the microwave for 10-20 seconds from room temp!