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

Heat the same pan over medium-high. When hot, add 1/2 tbsp oil (dbl for 4 ppl), 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 1/2 tsp vinegar (dbl for 4 ppl). Sprinkle flour over top. Cook, stirring constantly, until combined, 1 min. Add veggies from the medium bowl, broth concentrates and 3/4 cup water (dbl for 4 ppl). Bring to a simmer. Once simmering, cook, stirring often, until sauce thickens slightly, 1-2 min. Season with salt and pepper, to taste.

Transfer bison filling to an 8x8-inch baking dish (9x13 for 4 ppl). Unroll puff pastry and discard the wax paper. Lay puff pastry over top of filling, then crimp pastry edges to the sides of the baking dish. Brush top of pastry with melted butter, then sprinkle 1/4 tsp salt (dbl for 4 ppl) and remaining thyme over top. Using a knife, make 3 small slits into top of pastry (6 slits for 4 ppl). Place dish on an unlined baking sheet. Bake in the middle of the oven, rotating dish halfway through, until pastry is golden-brown and flaky, 20-25 min.

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

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