NOTE: THESE ARE MAKE-AHEAD FRIES, AS MCDONALD'S FRIES ARE PREVIOUSLY FROZEN BEFORE FRYING. ALLOW CUT, BRINED AND BOILED POTATOES TO FREEZE OVERNIGHT BEFORE FRYING. (STEP ONE): POUR 8 cups filtered water into a large saucepan; ADD 1 tablespoon fine sea salt, 1 teaspoon sugar, 1/2 teaspoon white pepper and 1/4 citric acid (or 1 1/2 teaspoons white vinegar) to make the BOILING BRINE.
PEEL 4 medium russet POTATOES; CUT potatoes into 1/4" shoestrings; PLACE cut potatoes into the brine in large saucepan; COVER saucepan.
BRING the BOILING BRINE with potatoes to a full boil; REDUCE heat to medium and boil for 7 minutes; DRAIN immediately and place onto absorbent paper; ALLOW to cool at room temperature.
HEAT deep-fryer with proper amount of oil (you don't need beef tallow for this step) to 360°F; PLACE 1/2 of the potatoes in deep-frying basket; GENTLY lower potatoes into hot fat; FRY only 60 seconds to sear; ELEVATE fry basket to drain for 30 seconds; IMMEDIATELY transfer fries single-layer over a rack-lined baking sheet to drain; ALLOW to cool to room temperature again.
ARRANGE cooled potatoes single-layer without crowding in ZIPLOC freezer bags; FREEZE potatoes overnight or up to one month.
TO DEEP-FRY (DO NOT STOVETOP FRY SINCE YOU NEED A PROPER BASKET TO SUPPORT FRIES AND ELEVATE FROM HEAT SOURCE): PREHEAT deep-fryer to 220°F with recommended amount of DEEP-FRYING FAT (100% grass-fed beef tallow).
LINE a baking sheet with paper towels.
RAISE heat of deep-fryer to 360°F (Maintain frying oil temperature using a deep-frying thermometer to gauge heat; PLACE 1/2 of the potatoes in deep-frying basket; GENTLY lower potatoes into hot fat; FRY between 3 - 3 1/2 minutes; ELEVATE fry basket to drain for 30 seconds; IMMEDIATELY transfer fries single-layer in a baking sheet.
SEASON french fries liberally with fine flake sea salt and eat immediately, or keep warmed for a limited time in a 200°F oven.
SERVE french fries with your favorite condiment and ENJOY!