In a small nonstick skillet, warm oil over medium heat. Add shallot; sauté until soft and lightly golden, about 4 minutes. Add garlic and sauté for 1 minute longer.
In a mini food processor, combine 1/4 cup pistachios and a pinch of salt; pulse until finely chopped. Add lentils, vinegar and shallot mixture; season generously with salt and pepper. Pulse to combine. Add 2 to 3 tsp. water; pulse until smooth. Transfer to a small bowl and stir in butter, parsley and thyme. Cover and refrigerate for at least 2 hours or up to overnight.
Just before serving, core and cut apple into thin wedges (about 24 pieces). Spread 1 tsp. pâté over each apple slice. Chop remaining pistachios, sprinkle over apple slices and serve.