Prepare the gravy:
In a small bowl, dissolve the cornstarch in the water and set aside.
In a large saucepan, melt the butter. Add the flour and cook, stirring regularly, for about 5 minutes, until the mixture turns golden brown.
Add the garlic and cook for a further 30 seconds.
Add the beef and chicken broth and bring to a boil, stirring with a whisk.
Stir in the cornstarch and simmer for 3 to 5 minutes or until the sauce thickens.
Season with pepper. Taste and add additional salt, if necessary, to taste.
Make ahead and re-warm or keep warm until your fries are ready.
For Deep-Fried Fries:
Prepare your potatoes and cut into 1/2-inch thick sticks.
Place into a large bowl and cover completely with cold water. Allow to stand at least one hour or several hours.
When ready to cook, heat your oil in your deep fryer or large, wide, heavy cooking pot to 300F.
Remove the potatoes from the water and place onto a sheet of paper towel. Blot to remove as much excess moisture as possible.
Add your fries to the 300F oil and cook for 5-8 minutes, just until potatoes are starting to cook but are not yet browned.
Remove potatoes from oil and scatter on a wire rack.
Increase oil temperature to 375F.
Once oil is heated to that temperature, return the potatoes to the fryer and cook until potatoes are golden brown.
Remove to a paper towel-lined bowl.
To Prepare Poutine:
Add your fried or baked fries to a large, clean bowl.
Season lightly with salt while still warm.
Add a ladle of hot poutine gravy to the bowl and using tongs, toss the fries in the gravy. Add more gravy, as needed to mostly coat the fries.
Add the cheese curds and toss with the hot fries and gravy.
Serve with freshly ground pepper. Serve immediately.
Torn chunks of mozzarella cheese would be the closest substitution for white cheddar cheese curds. Other cheddar doesn't impart the same flavor. Don't use grated cheese because you want the chunks of cheese in your gravy.