1. If you have bone-in chicken thighs, don’t panic: it’s not terribly difficult to remove the bones. Place a thigh skin down on a board and make an incision along the bone with a sharp knife. Using the tip of the knife and short shallow strokes, expose the bone along its length. Work your way around the both ends of the bone, making sure you cut out the socket around its ball; it needn’t be very tidy. Slide the knife underneath the bone and release it. Do the same with the remaining thigh.
2. Slice the garlic cloves quite thinly on a diagonal, if the cloves are small. Slice the chorizo into 2mm thick rings; you’ll want about 4 slices per one thigh.
3. Slide your finger under the skin of each thigh, making a pocket. Push about 6 slices of garlic and 4 chorizo rings evenly distributed under the skin of each piece. Season them with salt and smoked paprika on both sides.
4. Skin the tomatoes by scoring the tops crosswise and plunging them into boiling water for a couple of minutes. Drain and peel the skin off. Slice each tomato horizontally quite thickly to get about six slices for each piece of chicken. Remove some of the seeds and juice from the slices. Sprinkle them with salt and place on paper towels for a few minutes to drain the liquid.
5. Prepare two heavy frying pans or cast iron skillets (the one for the cooking also oven-safe). If the bottom of the pan that’s going to weigh the chicken down is not too clean, use a disc of parchment paper to cover the bottom. Place the chicken skin side down in one skillet and put it over high heat. Preheat the other skillet (this is optional; reduces the time in the oven) and place it (with or without parchment) over the chicken pressing it down.
6. When the chicken starts to sizzle, turn the heat down to medium. Cook the chicken for 10-15 minutes without moving until the skin is brown and crispy. In the meantime preheat the oven to 200C/400F/gas 6.
7. Lift the chicken from the skillet and turn off the heat. Place the tomato slices in the skillet, sprinkle the sage leaves over the tomatoes and place the chicken thighs skin side up on top of the tomatoes.
8. Roast in the oven for 10 minutes, remove and rest for another 10 minutes before serving.