Dice 220g butter into ½ inch cubes and freeze for at least 25 minutes or overnight (preferred).
Preheat the oven to 425°F (220°C). Season chicken thighs on both sides with 8 to 10g salt. Roast on a rack set in a sheet tray for 20 to 25 minutes.
While the chicken roasts, small dice onion, celery, carrot, leek and fennel. Press garlic and keep it separate.
Heat about 2 T neutral oil in a 12 inch cast iron pan over medium heat. Sweat the veg with a strong pinch of salt for 6 to 8 minutes without browning. Add garlic and cook for 1-2 more minutes.
Stir in 75g unsalted butter until melted, then add 75g flour and the poultry seasoning. Cook, stirring for 1 minute.
Deglaze with white wine and stir for 1 to 2 minutes.
Add chicken stock and Better Than Bouillon while stirring. Bring to a simmer, then drop to medium low and cook 3 to 4 minutes while scraping the bottom and corners.
When the chicken is cooked, pull it from the oven and allow it to rest for 5 minutes. Drop the oven temp to 400°F (205°C). Once rested, shred the chicken then run a knife through it to make 1 inch pieces. Off heat, stir the chicken, cream and frozen peas into the filling. Taste and adjust salt. Let cool for 5 to 10 minutes while you make the biscuits.
Pulse flour, sugar, baking soda, baking powder and salt in a food processor. Add the 220g frozen butter and pulse in short bursts about 20 times until the mixture forms lentil sized pieces. Transfer to a bowl then add cold buttermilk and stir gently with a spatula until a shaggy dough forms.
Drop 15-16 portions of 50g each around the edge of the skillet first, then fill in the center. Press each down slightly with the back of the spoon to create some texture on top of each piece of dough.
Set the skillet on a sheet tray and bake at 400°F (205°C) for 25 to 30 minutes until biscuits are deeply golden brown.
Rest for 10 minutes before serving.