https://www.authenticfoodquest.com/francesinha-recipe-portuguese-sandwich/

Note: this sandwich packs 3584 mg of sodium! The FDA recommends adults limit sodium intake to less than 2,300 mg per day.

Also note the site gives a lot of the background before the section "Francesinha Recipe – How To Make Porto Sandwich at home" and then it breaks up ingredients from instructions, and then near the very bottom gives complete instructions. The site has preparation pictures, which might be helpful. You will need:

Mortadella Ham
Mild Cheddar Cheese
Linguica Sausages

Ingredients For the sandwich

6 slices white ​​bread
2 tablespoons oil
½ pound beef fillet cut into two
½ pound ham
½ pound linguica sausages or chorizo
1 pound cheese to melt

For the sauce

1 small onion finely chopped, 70 g
2 tomatoes ripe, grated, without skin or seeds, 100 g
1 garlic clove crushed
1 bay leaf
1 tablespoon Peri Peri sauce
12 oz lager beer
3 tablespoons butter
1 cup beef broth
¾ cup Port wine
1 tablespoon fine cornflour or cornstarch
Salt and pepper to taste

For serving

French fries
2 eggs small

Instructions For the sauce

Place a small saucepan over medium heat on the stove top. Melt the butter and add the onion, garlic, and a little salt.
Cook until the onion is translucent and begins to brown. 

Immediately, add the crushed tomato, and the peri peri sauce. When the tomato is well cooked, add the beer, bay leaf, Port wine, and broth. Continue cooking uncovered for about ten more minutes. Dissolve the cornstarch in a quarter cup of water. And add it to the sauce. Cook for about five more minutes, stirring, until the sauce thickens. Strain or blend the sauce and then return it into the hot pot. Set aside.

For the filling

Season the steak with salt and pepper. 

Heat two tablespoons of olive oil in a frying pan and once hot, cook the steak for three minutes on each side. Make sure it browns a little. Cut the sausages in half, lengthwise, as this prevents them from curling up during cooking. Cook for three minutes on each side. Toast the slices of sliced ​​bread.

Assembling the francesinha

Place one slice of ​​bread on a plate and top with the sliced ham.
Place the steak on top of the ham. Trim the edges of any protruding pieces of meat.
Cover with another slice of ​​bread and top with sausages.
Finally, cover with another slice of ​​bread. Cover your sandwich with 6 to 8 slices of cheese. 

Repeat for the other sandwich. If desired, with a cookie-cutter, make a notch in the cheese at the top of the sandwich. Crack open a small raw egg and place in the opening. Preheat oven on broiler Put the plate of sandwiches quite close to the top and bake for about 3 minutes. Check regularly to make sure the cheese has only melted and not turned brown. Carefully remove the plate and transfer sandwiches to two plates. Pour warm sauce over each sandwich covering it entirely. Surround each sandwich with plenty of french fries and enjoy. Serve some additional sauce to use while eating your sandwich.

Notes If you have trouble keeping the cheese and meat in the place, hold together using toothpicks. The author at the site says they use extra-virgin olive oil for this recipe. You can use any vegetable oil as well.

Nutrition Serving: 1 | Calories: 1979kcal | Carbohydrates: 33g | Protein: 110g | Fat: 140g | Saturated Fat: 67g | Polyunsaturated Fat: 11g | Monounsaturated Fat: 45g | Trans Fat: 1g | Cholesterol: 576mg | Sodium: 3584mg | Potassium: 1430mg | Fiber: 2g | Sugar: 11g | Vitamin A: 4063IU | Vitamin C: 17mg | Calcium: 1683mg | Iron: 5mg