Sure, here's a sample diet plan for a 70kg and 1.90m vegan person who wants to gain muscle mass. To gain muscle mass, it's important to consume enough calories and protein to support muscle growth, while also engaging in regular strength training exercises. Monday: Breakfast - Oatmeal with almond milk, banana, and chia seeds (1 cup of oats, 1 banana, 1 tbsp chia seeds, and 1 cup of almond milk) Snack - 1 apple and 2 tbsp of peanut butter Lunch - Vegan burrito with brown rice, black beans, avocado, tomato, and lettuce (1 large tortilla, 1/2 cup brown rice, 1/2 cup black beans, 1/2 avocado, 1/2 tomato, and 1 cup lettuce) Snack - Smoothie with banana, spinach, and vegan protein powder (1 banana, 1 cup spinach, 1 scoop vegan protein powder, and 1 cup water) Dinner - Vegan lentil curry with quinoa (1 cup lentils, 1/2 cup quinoa, 1 cup mixed veggies, 1 cup vegetable broth, and spices to taste) Tuesday: Breakfast - Vegan protein smoothie with blueberries and chia seeds (1 scoop vegan protein powder, 1 cup blueberries, 1 tbsp chia seeds, and 1 cup almond milk) Snack - 1 pear and 1 oz of almonds Lunch - Vegan wrap with hummus, cucumber, and roasted red pepper (1 large tortilla, 2 tbsp hummus, 1/2 cucumber, and 1/2 roasted red pepper) Snack - Vegan protein bar Dinner - Vegan chickpea stir-fry with brown rice (1 cup chickpeas, 1 cup mixed veggies, 1/2 cup brown rice, and spices to taste) Wednesday: Breakfast - Tofu scramble with veggies (1/2 block of tofu, 1 cup mixed veggies, and spices to taste) Snack - Vegan protein smoothie with strawberries and almond milk (1 scoop vegan protein powder, 1 cup strawberries, and 1 cup almond milk) Lunch - Vegan quinoa salad with mixed veggies and avocado (1 cup cooked quinoa, 1 cup mixed veggies, 1/2 avocado, and dressing to taste) Snack - 1 orange and 2 tbsp of almond butter Dinner - Vegan lentil soup with mixed veggies (1 cup lentils, 1 cup mixed veggies, 1 cup vegetable broth, and spices to taste) Thursday: Breakfast - Vegan protein smoothie with mango and almond milk (1 scoop vegan protein powder, 1 cup mango, and 1 cup almond milk) Snack - Vegan protein bar Lunch - Vegan tofu sandwich with hummus, tomato, and lettuce (2 slices of whole grain bread, 1/2 block of tofu, 2 tbsp hummus, 1/2 tomato, and 1 cup lettuce) Snack - 1 banana and 1 oz of walnuts Dinner - Vegan black bean chili with quinoa (1 cup black beans, 1 cup mixed veggies, 1 cup vegetable broth, 1/2 cup quinoa, and spices to taste) Friday: Breakfast - Vegan protein smoothie with banana and almond butter (1 scoop vegan protein powder, 1 banana, 2 tbsp almond butter, and 1 cup almond milk) Snack - 1 pear and 1 oz of pistachios Lunch - Vegan lentil wrap with avocado and mixed veggies (1 large tortilla, 1 cup cooked lentils, 1 cup mixed veggies, and 1/2 avocado) Snack - Vegan protein bar Dinner - Vegan tempeh stir-fry with brown rice (1 cup tempeh, 1 cup mixed veggies, 1/2 cup brown rice, and spices to taste) Saturday: Breakfast - Vegan protein smoothie with mixed berries and almond milk (1 scoop vegan protein powder, 1 cup mixed berries, and 1 cup almond milk) Snack - 1 apple and 2 tbsp of cashew butter Lunch - Vegan lentil soup with mixed veggies (1 cup lentils, 1 cup mixed veggies, 1 cup vegetable broth, and spices to taste) Snack - Vegan protein bar Dinner - Vegan chili with mixed veggies and quinoa (1 cup mixed veggies, 1 cup kidney beans, 1 cup vegetable broth, 1/2 cup quinoa, and spices to taste) Sunday: Breakfast - Vegan protein pancakes with mixed berries (1 cup whole wheat flour, 1 scoop vegan protein powder, 1/2 cup almond milk, and 1 cup mixed berries) Snack - 1 orange and 1 oz of almonds Lunch - Vegan tempeh wrap with hummus, mixed veggies, and avocado (1 large tortilla, 1 cup tempeh, 2 tbsp hummus, 1 cup mixed veggies, and 1/2 avocado) Snack - Vegan protein smoothie with peanut butter and banana (1 scoop vegan protein powder, 1 banana, 2 tbsp peanut butter, and 1 cup almond milk) Dinner - Vegan lentil and vegetable stir-fry with brown rice (1 cup lentils, 1 cup mixed veggies, 1/2 cup brown rice, and spices to taste) In terms of exercise, a combination of strength training exercises that target major muscle groups such as squats, lunges, deadlifts, bench press, pull-ups, and rows can be effective for building muscle mass. It's also important to gradually increase the weight and intensity of these exercises over time to continue challenging the muscles and promoting growth.