Spring Bolognese - Spinach and Asparagus

Name: Spring Bolognese - Spinach and Asparagus
Cuisine: European, Italian, Mediterranean
Ingredients: 2 tbsp olive oil; 200g frozen spinach or baby leaf spinach; 1 onion, finely chopped; 300ml hot vegetable stock; 1 celery stick, finely chopped; 500ml passata; 1 x 400g tin of brown lentils, drained and rinsed; 4 servings of spaghetti (75g per person); 20g basil, stalks and leaves finely chopped; 200g asparagus (or purple sprouting or; Tenderstem broccoli), trimmed and roughly chopped; sea salt and black pepper