Line a 20cm (8 inch) square baking tin with baking parchment, allowing a little overhang on the sides for easy removal after baking. Lightly grease the tin then set aside.
Pre-heat the oven to 180°C / 160°C fan assisted / gas mark 4 / 350°F.
Combine the whole milk with the vinegar in a jug or bowl with a pouring spout. Stir briefly then rest for at least 5 minutes to allow the vinegar to curdle the milk.
Whisk together the dry ingredients (gluten-free flour, cornmeal, baking powder, bicarbonate of soda and salt) in a large mixing bowl.
Add the eggs, honey and melted butter into the milk mixture and whisk well.
Make a well in the dry ingredients and pour the wet ingredients in, whisking all the while until well combined.
Add the cheddar and chives and fold into the cornbread batter until combined. Finally gently stir in the sweetcorn kernels.
Pour the batter into the prepared baking tin and bake for 35 minutes until the top is golden brown.
Remove from the oven and sprinkle over the final 40g cheddar cheese and place back into the oven for a final 5 minutes.
The cornbread is ready when the cheese has melted and the bread is just starting to pull away from the sides of the tin. An inserted skewer should come out clean.
Allow the cornbread to rest in the tin for 10 minutes, before carefully removing. You can cool the bread on a wire rack or serve warm.