You hold: ♠J432 ♥KQJ ♦Q73 ♣Q95 and your partner opens 2♣. Do NOT bid 2NT with this hand. You do NOT want the weaker hand "grabbing" the NT. Bid a simple 2♦ waiting. Partner will rebid 3NT (showing 25-27 balanced.) You have 11, so your bid is 5NT—a quantitative raise, telling partner to bid 6NT with a minimum (25 HCP) and 7NT with a maximum (27 HCP or 26 that partner likes). The end result will be 6NT.
Partner: ♠AK7 ♥A4 ♦AK10 ♣AK872
You: ♠J432 ♥KQJ ♦Q73 ♣Q95
The lead is the ♥9. Correct play is to take the ♥A and cash the ♣A. The ♣10 appears on your right. Restricted choice says that the odds are roughly 2:1 that the ♣10 a singleton rather than the ♣10 from ♣J10 doubleton. If you have the courage of your convictions, you will play a low club to the ♣9 the next time and wrap up five clubs; three diamonds; three hearts and two spades, for all thirteen tricks. If you don't make use of restricted choice, you'll take only 12 tricks.
Hand #2 you hold ♠Q9 ♥AKQ86 ♦AK72 ♣A10 and partner opens a Weak Two bid in spades. You check for an outside Ace or King, and partner denies having any. You then check for Key Cards and partner shows you two Key cards which must be ♠A and the ♠K. You can now count 12 top tricks: six spades; three hearts; two diamonds and one club. So, if you are going to bid only a SMALL slam, you should bid 6NT for all the matchpoints. However, I strongly suggest that you consider bidding 7♠! If partner has ♦Q, you'll make a 13th trick easily. However, your heart suit is a SOURCE of tricks suit! If partner has a singleton heart, opponents hearts are likely to divide 4-3 and partner can ruff one round to set up your fifth heart for a 13th trick. If partner has two hearts, developing hearts is even easily; if partner has three hearts, developing hearts is almost guaranteed; only a highly unlikely 5-0 heart break (4%) would set you.