Ryote-jime (両手絞), the two-hand strangle.

Shime-waza (strangles).
Required for: 3rd Dan (black belt, British Judo Association); 4th Dan (black belt, British Judo Association); 5th Dan (black belt, British Judo Association).

About
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The strangle with both hands working as a pair: both fists grip the collars and drive together, knuckles turning in, like wringing a towel. Strangles are restricted by age in most federations; learn and practise this only under instruction and supervision.

Step by step (standard right-handed form)
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1. Facing your partner on the ground, grip both of their collars near the front of the neck, one in each fist, thumbs wrapped in the cloth.
2. Bring your fists close together so the collars are gathered at the front of their neck.
3. Turn both wrists so the little-finger edges of your fists rotate towards their neck, the cloth tightening around it.
4. Draw the fists towards each other and slightly towards you, on a smooth curve, like wringing.
5. Release both hands fully at the tap, and check your partner.

Key points
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1. Both fists grip the collars close together at the front
2. Turn the knuckles in and draw the fists towards each other
3. The action is a wring, applied gradually

Receiving it
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Both fists gather your collars at the front and the cloth wrings tight from both sides at once. Grip their wrists and tuck your chin before the wring settles. Tap immediately and clearly the moment the strangle is properly on, on their arm or body where they will feel it; never hold out to prove toughness. Tell your instructor if you ever feel light-headed afterwards.

Reference pages elsewhere
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Ryo-te-jime on the IJF technique reference (International Judo Federation): https://judo.ijf.org/techniques/Ryo-te-jime

From Waza Book: https://wazabook.com/techniques/ryote-jime/