Vegan slow cooker dumpling stew

Name: Vegan slow cooker dumpling stew
Ingredients: 2 tsp. vegetable oil; 1 large onion, finely chopped; 2 garlic cloves, crushed; 1 tbsp. tomato purée; 3 tbsp. plain flour; 150 mL vegan red wine; 2 carrots, cut into 1cm rounds; 300 g portobello mushrooms, sliced; 2 x 400g tins green lentils, drained and rinsed; 700 mL vegetable stock; Small handful thyme sprigs; 1 tbsp. Marmite, optional; Small handful fresh parsley, roughly chopped (optional); 100 g self-raising flour; 40 g vegan spread, chilled, we used Pure; 1 tsp. dried thyme