Prepare the chicken: Place each chicken breast on a cutting board. Using a sharp knife, carefully slice horizontally through the thickest part of the breast, stopping about 1cm from the opposite edge. Open the breast like a book — it should resemble a butterfly shape. Cover with a sheet of baking paper and gently pound with a rolling pin until the breast is an even 1cm thickness. The chicken should feel uniformly thin and look like a large, flat oval.

Cook the spinach filling: Heat a large frying pan over medium-high heat and add the olive oil. When the oil shimmers and you see gentle ripples across the surface, add the fresh spinach. You'll hear a satisfying sizzle as it hits the pan. Stir continuously with a wooden spoon for 2-3 minutes, watching as the leaves wilt down dramatically. The spinach will turn a deep, vibrant green and release its moisture. Once wilted, transfer the spinach to a clean tea towel and squeeze firmly to remove as much liquid as possible — you'll see the green water run out. Finely chop the squeezed spinach and place it in a mixing bowl.

Make the cheese mixture: To the bowl with the chopped spinach, add the softened cream cheese, grated mozzarella, grated Parmesan, and minced garlic. Stir everything together until you have a thick, cohesive paste. The mixture should be a pale green colour with visible flecks of spinach and Parmesan. Taste and adjust with a pinch of salt and pepper — it should be savoury and rich.

Stuff the chicken: Lay one butterflied chicken breast flat on the board. Spoon a quarter of the spinach and cheese mixture (about 3 tablespoons) onto the centre of the breast. Spread it evenly, leaving a 2cm border around the edges. Fold the top half of the chicken over the filling, pressing gently to seal. The breast should look like a plump, stuffed pocket with the filling peeking out slightly at the edges. Season the outside of each stuffed breast with salt, pepper, and a light dusting of smoked paprika.

Sear the chicken: In the same frying pan you used for the spinach, melt the butter over medium-high heat. When the butter stops foaming and smells nutty, carefully place the stuffed chicken breasts into the pan, seam-side down. You should hear a loud, consistent sizzle — that's the sound of a good sear. Cook for 4-5 minutes without moving them, until the underside is a deep golden brown with visible caramelisation. Using tongs, flip each breast gently. The cooked side should release easily from the pan; if it sticks, give it another 30 seconds.

Finish cooking: Pour the chicken stock into the pan around the breasts — it will bubble up immediately, creating steam. Reduce the heat to medium-low, cover the pan with a lid, and let the chicken cook for 12-15 minutes. During this time, the kitchen will fill with a savoury, buttery aroma. To check doneness, insert an instant-read thermometer into the thickest part of a breast without touching the filling — it should read 74°C. The chicken will feel firm to the touch but still give slightly when pressed.

Rest and serve: Transfer the cooked chicken breasts to a cutting board and let them rest for 5 minutes. This is crucial — you'll see the juices redistribute as the chicken relaxes. Slice each breast on a diagonal to reveal the beautiful green and white spiral of the filling. The cheese should be molten and slightly oozing, and the chicken should be moist and tender. Garnish with fresh thyme sprigs if desired.