In a frying pan, on medium to high heat add butter, once melted, reduce to low heat, add chicken, sauté until fully cooked, add onion, sauté until translucent, add garlic, sauté until fragrant, add red pepper and spinach, sauté until wilted, then add salt, pepper, and chicken Bovril, mix until combined. Remove from heat and let cool.
In a bowl, add chicken mixture, cream cheese and mozzarella. Drain any excess liquid.
Unfold Puff Pastry on a clean surface, cut into 8 pieces, add a spoon of chicken spinach filling in the centre of each leaving room to fold, fold over and crimp edges with fork. Repeat process for the other puff pastry sheet.
Place on a baking sheet lined with parchment paper, bake at 375 degrees for 30 minutes, until golden brown.