Photograph: Jonathan Gregson
Preheat the oven to 200°C, 180°C fan, gas 6. Dry-fry the chorizo until crisp, remove to a bowl using a draining spoon and leave to cool. Melt the butter in a small pan and set it aside. Halve the tomatoes, remove and discard the seeds, then chop the tomato flesh.
Using a balloon whisk and a large mixing bowl, whisk together the milk, yogurt, eggs, olive oil and melted butter to a batter. Don't worry if you have a few small, stubborn blobs of yogurt.
Sift in the flour and baking powder. Add a pinch of salt and scatter the chorizo, chopped tomatoes, sweetcorn and thyme over the top. Using a large metal spoon, fold everything together until combined, but don't overmix. Divide the mixture among an oiled 6-hole muffin tin, piling them up high. Sprinkle a few oats on top of each one.
Bake the muffins for 20-25 minutes. Cool for 15 minutes in the tin. Loosen around the edges of each muffin with a knife, then tip each one out of the tin on to a cooling rack. Serve warm or cold.