In a large pot of salted boiling water, cook spaghetti according to package directions until al dente. Drain then Rinse with water and then drizzle some oil on it so that they will not stick together.
Meanwhile, in a large heavy bottomed skillet over medium-high heat, heat oil. Add ginger garlic paste then shrimp and season with ¾ teaspoon salt and ½ teaspoon peppers and chili flakes. Cook, tossing occasionally, until shrimp is pink and just cooked through, about 4 minutes. Add 2 tablespoons lemon juice and toss to coat. Remove shrimp from skillet and reserve on a plate.
In the same skillet over medium-high heat, melt butter. Add garlic and cook until fragrant, 30 seconds then add in your chopped vegetables by seasoning it with some salt and pepper. Cook until sauteed.. Remove vegetables from skillet and reserve on a plate.
In the same skillet over low heat, melt butter. add in flour mix well then add the milk then season it with salt and peppers and cook until it thickens. For making it more gooey and yummy you can also add some mozzarella or cheddar cheese in it .
Take some oil in pan add in the tomato puree and cook it for few minutes . Then sprinkle the spices and some ketchup or tomato paste , cook until desired consistency . It should not be too thick or thin You can also add some hot sauce or buffalo sauce or Peri Peri sauce to it , according to your taste.
Add cooked pasta and shrimp to skillet and vegetables and both sauces toss to coat. Season to taste with more salt and pepper. Garnish with parsley and green onions with some sprinkle of Mozzarella.