Before starting, preheat the oven to 425°F. Wash and dry all produce. Add 1 tbsp butter (dbl for 4 ppl) to a large non-stick pan. Melt over medium-high heat. Transfer melted butter to a small bowl. While butter melts, strip 2 tsp thyme leaves (dbl for 4 ppl) from stems, then finely chop. Peel, then mince or grate garlic.

Heat the same pan over medium-high. When hot, add 1/2 tbsp oil (dbl for 4ppl), then mirepoix. Season with salt and pepper. Cook, stirring occasionally, until veggies soften slightly, 2-3 min. Add garlic, peas and half the thyme. Cook, stirring often, until fragrant, 1 min. Transfer veggies to a medium bowl.

Heat the same pan over medium-high. When hot, add 1 tbsp butter (dbl for 4 ppl), then bison. Cook, breaking up bison into smaller pieces, until no pink remains, 4-5 min. Season with salt and pepper. Stir in tomato sauce base and Worcestershire sauce. Sprinkle flour over top. Cook, stirring constantly, 1 min. Add veggies from the medium bowl, broth concentrate and 1 cup water (dbl for 4 ppl). Bring to a boil. Cook, stirring often, until sauce thickens slightly, 1-2 min. Season with salt.

Transfer bison filling to an 8x8-inch baking dish (9x13-inch for 4 ppl). Unroll puff pastry and discard the wax paper. Lay puff pastry over top of filling, then crimp edges of puff pastry to side of baking dish. Brush the top of pastry with melted butter, then sprinkle with 1/4 tsp salt (dbl for 4 ppl) and remaining thyme. Using a knife, make three small slits into top of pastry (6 slits for 4 ppl). Place dish on a baking sheet. Bake in the middle of the oven, rotating the dish halfway through, until pastry is golden-brown and flaky, 20-25 min.

While pie bakes, halve grapes. Whisk together vinegar, 1/8 tsp sugar and 1 1/2 tbsp oil (dbl both for 4 ppl) in a large bowl. Season with salt and pepper. When pie is almost done, add grapes and arugula and spinach mix to the bowl, then toss to combine.

Allow pie to rest 3-5 min. Divide pie between plates. Serve salad alongside.