Prepare the brown rice by cooking it in an instant pot, slow cooker, or according to package instructions if already cooked. If making from scratch, use a ratio of 2 cups water for every 1 cup of rice. Bring to a boil, then simmer covered for about 40 minutes until tender. Keep extra rice in the fridge for other meals, as cooked rice stores and freezes very well.
Preheat the oven to 425°F (220°C). Peel and dice the butternut squash into 1/2-inch cubes. Toss the cubes with 1 tablespoon of olive oil, 1/4 teaspoon kosher salt, and 1/8 teaspoon black pepper (or to taste). Spread evenly on a baking sheet and roast for 20 to 30 minutes, flipping halfway through, until golden and tender.
In a small food processor, combine the bunch of parsley, ripe avocado, 1/4 cup olive oil, 2 tablespoons fresh lemon juice, 1/4 teaspoon kosher salt, and 1/8 teaspoon freshly ground black pepper. Pulse until the mixture reaches a pesto-like consistency. Add water by the tablespoon as needed if the sauce is too thick. For extra flavor, I sometimes add a garlic clove or a teaspoon of garlic powder.
Heat a dry skillet over medium heat. Add the sliced almonds, stirring frequently, until they turn golden brown and fragrant, about 3-4 minutes. Don't walk away, as nuts can burn quickly! I find that toasting the almonds really brings out their flavor and adds the perfect crunch to the bowl.
Clean the mushrooms by rinsing off any dirt, then dry well with a paper towel. Slice them 1/4 inch thick. Heat 1 tablespoon olive oil in a medium-sized pan over medium-high heat. Once hot, add the mushrooms in a single layer. Cook until they are well browned on one side, then flip and brown the other side, about 5-7 minutes in total.
To plate, start by placing the cooked brown rice (from Step 1) at the bottom of a bowl. Top with roasted butternut squash (from Step 2), sautéed mushrooms (from Step 5), herby avocado sauce (from Step 3), toasted almonds (from Step 4), and sprinkle with feta cheese for a creamy, salty finish.